10 Best Mainframe Modernization Companies to Trust in 2026

According to IBM, mainframe technology is still used by 45 of the top 50 banks and 67 of the Fortune 100 companies.

These systems support critical workloads, which makes their stability essential.

However, because many are built on legacy infrastructure, they also introduce risks such as unexpected outages, security gaps, and potential loss of market share if not properly maintained.

As a result, decision-makers are increasingly aware of the limitations of legacy systems. In fact, nearly 90% of decision-makers believe legacy systems are holding their organizations back in terms of growth and operational efficiency.

The shortage of skilled mainframe professionals further increases risk and slows down transformation efforts.

To address these challenges, enterprises are actively investing in modernization initiatives. Organizations that have modernized their mainframe systems are already seeing measurable improvements.

For example, in the insurance sector, modernization has reduced claim cycle times from 7 days to under 48 hours.

In financial services, firms have achieved sub-10 millisecond trade execution latency through legacy application modernization.

These outcomes demonstrate the vital role of mainframe modernization for enterprises in 2026.

Mainframe modernization is not limited to a single industry. Multiple sectors rely on mainframes for critical operations and are actively looking to hire top companies for mainframe modernization to stay competitive.

Some of the top sectors are:

• Banking and Financial Services

BFSI dominated the mainframe modernization market with 32% market share in 2024. Banks and the fintech sector rely on mainframes for core banking, transaction processing, and regulatory compliance.

Mainframe modernization services enable real-time payment processing, open banking integration, and improved fraud detection while maintaining system stability and compliance.

• Healthcare

The healthcare industry uses mainframes to manage patient records, billing systems, and clinical data. These legacy systems limit interoperability and real-time data access.

Modernization helps integrate electronic health records with digital platforms, support telemedicine, and enable data-driven care models required for value-based healthcare.

• Insurance

Insurance providers depend on mainframes for policy administration and claims processing at scale. Legacy environments slow down product launches and limit customer experience.

Mainframe service providers modernize outdated systems to help insurers automate underwriting, deliver instant quotes, and integrate with digital distribution channels.

• Government

Government agencies run large-scale systems for social services, taxation, and public records on mainframes. These systems must remain highly reliable while serving millions of users.

The top mainframe companies help organizations modernize their systems to improve citizen services, enable digital portals, and reduce the risk of system failures that can affect millions of people.

• Retail and E-Commerce

In the retail sector, mainframes are used for inventory management, order processing, and supply chain operations. However, legacy systems struggle to support real-time data synchronization across channels.

Mainframe modernization helps retailers connect these systems to e-commerce platforms, enabling omnichannel experiences and real-time inventory visibility across physical and digital channels.

Choosing the best-rated mainframe modernization company is not just a vendor selection decision. It is a multi-year architectural commitment that impacts core systems, regulatory obligations, and enterprise competitiveness.

Getting it wrong costs more than the project budget. It leads to operational disruption, technical debt, and long-term loss of time and investment.

To evaluate the top companies for mainframe modernization, it is important to assess them across technical, strategic, operational, and risk-related dimensions:

Consider the following factors to partner with the right modernization partner:

Not all mainframe service providers carry the same depth.

Some firms handle COBOL migrations competently but struggle with PL/I, Assembler, and proprietary transaction engines, such as CICS and IMS.

The right partner understands the business logic embedded in decades-old code and preserves it during modernization.

Ask for concrete examples of systems they have modernized, including scale, complexity, and outcomes.

Some mainframe modernization vendors recommend moving everything to the cloud regardless of whether it fits. Others default to rehosting because it is faster to sell and easier to deliver.

The best mainframe modernization companies take a contextual approach.

They determine whether rehosting, refactoring, or a hybrid approach best fits the system and business goals.

If a provider avoids recommending lower-cost or simpler mainframe modernization techniques, it may indicate a focus on their profits over your results.

Modern mainframe transformation cannot rely on manual processes. Large-scale code analysis, refactoring, and testing require automation to reduce risk and improve consistency.

Evaluate whether the vendor uses AI-assisted code analysis, automated migration tools, and regression testing frameworks.

Certified mainframe modernization experts who invest in modernization accelerators typically deliver faster timelines, lower defect rates, and more predictable outcomes compared to manual-heavy approaches.

Mainframe modernization case studies highlight success, but they rarely show the full picture.

To properly evaluate a vendor, look for references from organizations in your industry and speak to the people who were directly involved in the project.

Ask what challenges occurred during delivery, how they were resolved, and whether the organization would choose the same legacy mainframe modernization partners again.

These conversations provide more reliable insight than any polished case study.

Modernization does not end at go-live. Performance tuning, security patching, and continued refactoring continue for months after the initial migration.

It is important to understand what post-launch support is included, how it is structured, and whether the same engineering team continues to support the system after go-live.

Continuity of technical teams plays a critical role in maintaining stability and reducing operational risk.

Mainframe systems handle sensitive data, including financial transactions, customer records, and critical business operations.

Any vendor you consider must meet strict security and compliance standards. Review their security certifications, development practices, and data protection processes.

ISO 27001 and SOC 2 are baseline requirements. More importantly, check whether the vendor has experience with your regulatory environment, such as HIPAA or PCI-DSS.

This experience helps reduce risk, meet audit requirements, and keep the modernization project aligned with industry regulations.

IBM’s position on this list comes with an important caveat.

No mainframe modernization company understands the internals of mainframe architecture the way IBM does.

That knowledge creates real advantages for organizations that are not planning a full cloud exit and want to modernize while staying on IBM Z infrastructure.

Their Z Transformation Tools support automated code analysis, DevOps integration, and hybrid cloud connectivity without requiring a platform change.

For organizations that have built compliance workflows, regulatory reporting, and transaction processing directly into mainframe architecture, incremental modernization on the platform itself is sometimes the right call.

That said, IBM’s scale means engagement models are standardized.

Organizations with complex, non-standard requirements may find the process less flexible than smaller, specialized firms.

Perfect For

Organizations committed to IBM Z infrastructure that want incremental modernization and deep platform-level tooling without migrating to a third-party cloud.

Key Services

• Hybrid cloud mainframe modernization
• IBM Z systems optimization
• Automated code migration
• Advanced analytics and AI integration

Company Overview

• Team Size: 10001+ employees
• Location: Armonk, NY, USA
• Founded: 1911

Code District takes the top spot on this list because they cover the full modernization lifecycle without forcing a single approach.

Code District begins with an assessment of the existing system instead of applying a fixed modernization approach.

This is important for legacy environments where core business logic is deeply embedded and cannot be moved or rehosted without analysis.

The company works across COBOL, PL/I, and legacy application re-architecture. It also integrates mainframe systems with cloud services through APIs and enables AI features where relevant to the use case.

An example of this approach is the SwatFame legacy system modernization case study, where fragmented Visual Basic 6 systems were consolidated into a unified Azure platform.

The company helped SwatFame automate 90% of its manual workflows and improve order processing speed by 40%.

Code District holds ISO 9001 and ISO 27001 certifications, is an AWS Partners, and is a member of the Forbes Business Council.

Code District earned a spot on the 2025 Inc. 5000 list of Fastest-Growing Companies, reflecting its proven track record of helping enterprises transform legacy systems.

Perfect For

Mid-size to large enterprises that need a partner willing to recommend the right approach, even when it is not the most profitable one for the vendor.

Key Services

• End-to-end mainframe modernization solutions
• COBOL, PL/I, and legacy application re-architecture
• Cloud-ready solutions for hybrid cloud environments
• Custom-tailored mainframe modernization strategies
• Automated code refactoring and testing
• Post-modernization support and optimization

Company Overview

• Team Size: 250-999 employees
• Location: Washington, DC, USA
• Founded: 2017

Astadia strongly focuses on mainframe-to-cloud migration and related mainframe modernization services.

Its FastTrack Migration Factory uses automation to support code conversion, data migration, and testing across large-scale modernization projects.

The platform helps reduce manual effort and improve consistency across complex migration programs by industrializing key stages of the process.

Astadia supports major mainframe environments, including IBM z/OS and legacy systems built in COBOL, Assembler, Natural, and Adabas, as well as Unisys-based workloads in applicable projects.

The company has delivered modernization projects across financial services, insurance, government, and transportation sectors.

Here is the SD Worx case study, where COBOL-based applications were running on an IDMS database optimized for long-running batch workloads.

Astadia used its FastTrack Migration Factory to migrate the database from IDMS to DB2 and convert Enterprise COBOL to Micro Focus COBOL off the mainframe.

Perfect For

Large enterprises in financial services and government that need an automation-first migration with documented functional equivalence.

Key Services

• Mainframe-to-cloud migration
• Application replatforming
• Automated legacy code conversion
• Hybrid modernization strategies

Company Overview

• Team Size: 501-1000 employees
• Location: Fort Lauderdale, FL, USA
• Founded: 1996

Micro Focus provides comprehensive COBOL refactoring and rehosting tools that enable organizations to modernize without complete rewrites.

Their Enterprise Suite enables COBOL applications to run on cloud platforms by recompiling and rehosting existing code rather than converting them to another language.

That approach reduces migration risk and shortens timelines, but it also means the underlying application logic stays largely unchanged.

If your priority is getting off the mainframe quickly while preserving existing code, this model works. If your goal is long-term architectural change, you will likely need additional work after the initial migration.

Perfect For

Organizations that want to rehost with minimal code changes and plan to refactor gradually after the initial migration.

Key Services

• COBOL refactoring and cloud integration
• Automated testing and validation
• Mainframe rehosting solutions
• Security and compliance for regulated industries

Company Overview

• Team Size: 10001+ employees
• Location: Newbury, UK
• Founded: 1976

Accenture ranks among the top companies for mainframe modernization due to its scale and depth across industries, which most specialized modernization firms cannot match.

Their myNav assessment platform analyzes application portfolios and recommends modernization paths before a single line of code is touched.

That front-end rigor reduces the discovery surprises that derail mid-project timelines.

They also go beyond technical modernization.

Process reengineering and organizational change management are built into their delivery model, which matters when the real obstacle to adoption is not the technology.

The tradeoff is cost and standardization.

Accenture projects come with significant overhead, and smaller or mid-market organizations often find themselves deprioritized compared to Fortune 500 engagements.

Perfect For

Fortune 500 companies seeking holistic transformation across technology, processes, and organization.

Key Services

• Enterprise-level replatforming
• AI and automation integration
• Comprehensive digital transformation
• Industry-specific modernization strategies

Company Overview

• Team Size: 10001+ employees
• Location: Dublin, Ireland (Global operations)
• Founded: 1989

Corsac Technologies ranks among the top companies for legacy software modernization due to its 18-year focus on regulated and mission-critical systems.

Their AI modernization platform turns unpredictable legacy modernization into a controlled, measurable process.

Built on a RAG architecture with multi-agent code analysis, it delivers: automated dependency mapping that eliminates months of reverse engineering; minimized risk through dependency isolation; predictable timelines with measurable milestones; behavioral parity with the original system; and zero-downtime upgrades via canary deployments and automated rollback.

Corsac plugs into the client’s existing Git, CI/CD, and engineering workflows rather than running a parallel project. The in-house team keeps shipping while Corsac drives the transformation, evolving what’s stable and replacing only what blocks growth.

Perfect For

Mid-market and enterprise organizations in regulated sectors that need legacy modernization under HIPAA, GDPR, SOC2, ISO27001, or HL7/FHIR frameworks without disrupting their in-house engineering team.

Key Services

• Legacy software modernization
• Software migration
• Cloud and data modernization
• Code re-engineering

Company Overview

• Team Size: 50-240 employees
• Location: Toronto, Canada
• Founded: 2007

TSRI provides an automated COBOL-to-Java transformation that preserves business logic while modernizing codebases.

Their platform converts COBOL to Java or C# by analyzing and preserving embedded business logic during the transformation, rather than performing a line-by-line syntax swap.

That distinction matters for organizations with decades of business rules encoded in their legacy code.

The limitation is the scope. TSRI excels at the translation phase.

Organizations that also need cloud architecture design, post-migration optimization, or ongoing managed services will need additional enterprise mainframe modernization vendors.

Perfect For

Organizations whose primary obstacle is the speed of language conversion and that have the internal capacity to manage architecture and post-migration work.

Key Services

• Automated code translation (COBOL to Java, C#, etc.)
• API generation for modern integration
• Cloud migration support
• Code analysis and refactoring

Company Overview

• Team Size: 11-50 employees
• Location: United States
• Founded: 1995

Raincode focuses on COBOL compilation to .NET and JVM platforms, enabling a gradual modernization approach.

Their compiler technology allows organizations to run existing mainframe code in modern environments without a full rewrite.

That makes it possible to modernize in phases, reducing the risk associated with replacing everything at once.

The incremental model suits organizations that cannot afford extended downtime or a single large-scale migration event.

Perfect For

Organizations seeking incremental, lower-risk modernization approaches.

Key Services

• COBOL to .NET/JVM compilation
• Legacy system refactoring
• Hybrid cloud migration
• DevOps workflow integration

Company Overview

• Team Size: 51-249 employees
• Location: Brussels, Belgium
• Founded: 1998

CloudFrame automates the transformation of monolithic mainframe applications into microservices.

Their platform breaks legacy applications into independently deployable components and integrates directly with DevOps pipelines for continuous modernization rather than a one-time cutover event.

That architecture suits organizations moving toward container-based deployment and seeking the ability to update individual services without touching the whole system.

Perfect For

Organizations modernizing toward microservices architectures and container-based deployment.

Key Services

• Microservices transformation
• Cloud-native deployment
• DevOps integration
• API-first architecture

Company Overview

• Team Size: 51-249 employees
• Location: New York, NY, USA
• Founded: 2017

Endava brings agile methodology to mainframe modernization, with particular experience in financial services and retail.

Their delivery model emphasizes continuous improvement after go-live, which means post-migration optimization is built into the engagement rather than treated as a separate contract.

That approach suits organizations that expect the modernized system to keep evolving rather than remaining static after the initial migration.

The firm’s geographic reach and multi-sector experience give it flexibility across European and North American markets.

Perfect For

Organizations in finance, retail, and telecom seeking agile transformation methodologies.

Key Services

• Mainframe replatforming
• Agile cloud transformation
• DevOps enablement
• Continuous system optimization

Company Overview

• Team Size: 10001+ employees
• Location: London, UK
• Founded: 2000

Ready for mainframe modernization?

Every modernization project is different. The right choice depends on your architecture, constraints, and business priorities.

Speak with a mainframe modernization expert to validate your decision before you move forward.

Mainframe modernization strategies define how enterprises transform legacy systems into modern, cloud-compatible architectures while preserving critical business operations.

The right strategy depends on:

• How much of the existing codebase can be preserved
• How much operational risk the organization can absorb
• The target architecture (cloud, hybrid, or microservices)

Top companies for mainframe modernization assess these factors before recommending the best migration strategy.

Rehosting moves mainframe workloads to modern infrastructure without changing application code.

It is commonly used when enterprises want to exit legacy mainframe hardware quickly while minimizing migration risk.

The primary benefit is speed, since the code remains untouched.

The limitation is that rehosting does not address technical debt.

However, rehosting does not reduce technical debt, and applications retain the same limitations in scalability, integration, and modernization capability.

It is typically used as an initial phase in a broader modernization roadmap rather than a final architecture.

Replatforming moves legacy workloads (often COBOL-based) to modern infrastructure with minimal code changes. It allows leveraging cloud-native capabilities such as autoscaling and managed services.

Unlike rehosting, replatforming modifies parts of the application to better align with the target environment.

It is used when enterprises want improved performance and cloud benefits without a full rewrite.

The main risk is scope expansion due to hidden dependencies and complex legacy integrations.

Automated analysis tools used by mainframe modernization companies help reduce this risk before migration begins.

Refactoring restructures existing code to improve maintainability, performance, and cloud compatibility while preserving core business logic.

It is commonly used for legacy COBOL systems where the business logic is valid, but the codebase has become difficult to maintain.

The main challenge is time, as deep code analysis is required before transformation begins.

It is not suitable when the business logic itself is outdated or misaligned with current operational needs.

Rearchitecting breaks monolithic mainframe systems into modern architectures such as microservices or event-driven systems.

It is used when incremental modernization is no longer sufficient for scalability, integration, or cloud-native adoption.

It delivers the highest flexibility among modernization strategies.

However, it is also the most complex approach because it requires a full understanding and redesign of embedded business logic.

Best mainframe outsourcing companies recommend this approach only when legacy systems have reached architectural limits.

Rebuilding replaces the existing application entirely while preserving functional requirements.

It is used when legacy systems are too fragmented, undocumented, or technically constrained for refactoring or incremental modernization.

The benefit is a clean, modern system built on current frameworks with no inherited technical debt.

However, rebuilding carries the highest execution risk due to challenges in ensuring functional parity with legacy systems.

It is considered only after other modernization strategies have been evaluated.

Hybrid modernization combines multiple strategies across different systems based on risk, complexity, and business criticality.

For example, batch systems may be rehosted, while customer-facing applications may be rearchitected within the same modernization program.

It is the most widely used approach in enterprise environments because most mainframe ecosystems are not uniform.

The main challenge is coordinating across multiple modernization tracks, which requires governance, testing, and integration planning.

API enablement exposes mainframe functionality through modern APIs without changing the underlying system.

It is commonly used when enterprises want to connect legacy systems to cloud applications, mobile platforms, or digital services.

It is used in banking and financial services where core transaction systems must remain stable while enabling digital access layers.

The limitation is that it does not address underlying technical debt or reduce long-term maintenance costs.

The best mainframe migration companies view it as a transitional modernization strategy rather than a final state.

Mainframe modernization is a long-term architectural decision that directly impacts cost, risk, and scalability across the enterprise.

The companies in this list differ in how they execute modernization, ranging from rehosting and replatforming to refactoring and full rearchitecture.

Because of this variation, the outcome depends less on mainframe modernization tools and more on how well a provider aligns with your system complexity and business goals.

Most enterprises can narrow down their options based on the technical depth, execution capability, modernization strategy, automation maturity, and long-term support a mainframe modernization company provides.

Ready to partner with a mainframe modernization company and avoid the $370M annual cost of legacy inefficiencies? Let Code District modernize your outdated systems.

Code District is an award-winning legacy system modernization company that is known among global clients for its affordable services and on-time project delivery.

We focus on protecting your data from unauthorized access and corruption during modernization. The ISO 27001 and ISO 9001 certifications testify to our commitment to data security and privacy.

Get in touch for a free consultation on modernization, and learn how it could benefit your business.