Top 10 Legacy Modernization Companies Powering Enterprise Transformation

The cost of maintaining legacy applications doesn’t always show up in quarterly results, but its impact compounds silently, draining agility, exposing risk, and limiting innovation.

The disconnect between legacy IT architectures and modern business models has now become too wide to ignore. From COBOL-based mainframes to aging ERP systems and tightly coupled client–server platforms, many foundational systems are now incompatible with cloud-native operations, real-time analytics, or AI-led transformation.

The ISG Provider Lens™ Mainframes – Services & Solutions 2025 (U.S.) report reflects this urgency. Enterprises are no longer asking whether to modernize, but how—and how quickly. ISG observes a marked shift in strategy: where once the focus was on cost-driven replatforming, leaders are investing in full application reengineering to unlock scalability, improve time-to-market, and enable data-driven innovation.

This blog draws from ISG’s analysis to profile ten of the top application modernization companies helping enterprises address outdated systems through automation, AI augmentation, and outcome-focused delivery. It also explores the pathways, pitfalls, and partner traits that define successful modernization at scale.

Why Modernize Legacy Systems Now?

While the terms are often used interchangeably, it is important to distinguish between the two. Mainframe modernization refers primarily to updating infrastructure platforms—like z/OS, iSeries, or hardware dependencies—while application modernization focuses on transforming the business logic, architecture, and codebase within those environments. This blog, and the ISG quadrant it draws from, is centered on application modernization: the layer where value is created through agility, automation, and future-ready design.

Modernizing legacy systems is no longer optional—it is a strategic imperative. A modern digital strategy is difficult to execute on 30-year-old foundations. Here are four pressure points pushing CIOs to act decisively.

• Rising Operating Expense
  Mainframe licensing models, indexed to MIPS or MSUs, escalate with transaction growth. When combined with proprietary middleware, periodic hardware refreshes, and niche support contracts, total cost of ownership rises steadily.

• Increasing Cyber Risk
  End-of-support operating systems and outdated encryption ciphers expand the attack surface. According to recent research, it takes an average of 258 days for security teams to identify and contain a data breach, highlighting the need for modern security capabilities. Regulators and insurers now scrutinize legacy environments for evidence of patch management and vulnerability mitigation.

• Innovation Bottlenecks
  Modern customers expect omnichannel engagement, real-time data, and rapid feature releases. Legacy platforms, designed for batch processing, slow integration efforts and complicate API strategies. A study found that retail banks running batch-based core systems experienced significant declines in Net Promoter Scores (NPS) when applications took more than 20 minutes to complete, highlighting the impact of outdated systems on customer satisfaction. 

• Talent Shortages
  Universities rarely teach older languages such as COBOL, Natural Adabas, PL/SQL, etc., and many experienced engineers are transitioning to retirement. Recruiting or retaining expertise for legacy troubleshooting has become progressively more difficult and expensive.

Delay adds to these challenges. Taking bold actions helps organizations redirect resources from maintenance toward innovation and growth.

How Enterprises Modernize: Five Strategies for Legacy Transformation

Before selecting a partner, organizations should understand the technical options available to them.

• Encapsulation: Introducing APIs or micro-frontends around existing legacy systems to expose functionality for digital channels without re-architecting the core
• Rehosting: Moving legacy applications to cloud infrastructure, often chosen when datacenter leases expire or hardware reaches end-of-life
• Replatforming: Upgrading the OS or database stack to reduce licensing costs and improve scalability—such as transitioning from UNIX to Linux, or Oracle to PostgreSQL
• Refactoring or Re-architecting: Decomposing monoliths into microservices, often using DevSecOps and containerization
• Rebuilding or Replacing: Rewriting applications or adopting SaaS platforms when the business logic itself is outdated

Most enterprises blend these approaches across different workloads, leveraging GenAI to accelerate everything from discovery and documentation to code conversion and testing.

Leading Legacy Modernization Companies to Consider

The following service providers have been recognized as “leaders” for their capabilities in application modernization:

1. Accenture: Enables large-scale modernization through AI-assisted code analysis, cloud-native frameworks, and deep domain knowledge. Transformation playbooks support phased execution, helping enterprises replatform or reengineer legacy estates while preserving business continuity
2. Capgemini: Applies automation and AI to streamline legacy code extraction, refactoring, and optimization. Modernization frameworks are adaptable across industries, embedding performance analysis and sustainability goals into delivery
3. DXC Technology: Delivers modernization with structured portfolio diagnostics and platform-aware migration models. Simplifies rehosting and refactoring through DevOps integration while minimizing downtime and operational risk
4. HCLTech: Accelerates reengineering using GenAI tooling and the AI Force™ platform. Flexible engagement models—from innovation labs to co-delivery—support transformation across regulated and high-availability environments
5. Hexaware Technologies: Accelerates legacy modernization with RapidX^®, a GenAI platform that creates AI-based SMEs for seamless knowledge transfer. Its toolset enables fast discovery, automated code refactoring, and smooth integration with CI/CD and partner platforms. By prioritizing high-impact projects, Hexaware delivers quick results and reinvestable gains for continuous transformation.
6. Infosys: Combines AI-powered diagnostics, the A.R.T. framework, and platform orchestration to guide transformation. Strong ecosystem partnerships and delivery maturity enable enterprise-scale application modernization aligned to cloud strategies
7. Kyndryl: Integrates telemetry insights with deep platform knowledge to guide hybrid modernization. Modular service models and design-led planning help enterprises transition core systems without loss of control
8. LTIMindtree: Delivers modernization through a modular, composable approach that integrates leading ecosystem tools. Phased execution and blueprint-driven delivery suit organizations evolving legacy architectures iteratively
9. Mphasis: Offers modernization as part of a self-funding model embedded in application services. Emphasizes automation, rationalization, and cost control to reduce technical debt without major upfront investment
10. Tata Consultancy Services (TCS): Executes high-complexity modernization through the MasterCraft™ automation suite and vertical accelerators. Combines secure migration, parallel testing, and domain expertise to support full-stack reengineering

The Hexaware Approach 

One of the leading application modernization companies, Hexaware offers modernization services along six approaches—rehost, replatform, re-architect, rebuild, replace, and run (continuous optimization)—and augments each approach with proprietary automation:

• RapidX^®uses generative AI to analyze legacy applications by decoding source code and mapping complex system dependencies. Through AI-driven assessment and optimization recommendations, it accelerates the initial modernization phase significantly.
• Amaze^®automates code conversion and data migration tasks, accelerating cloud deployment while enforcing quality and security controls.
• Tensai^®provides a low-code DevSecOps framework with integrated policy checks, facilitating secure continuous integration and delivery from the first migrated release.

For example, Hexaware partnered with a UK-based global shipping services provider to modernize its infrastructure to enable real-time tracking of 50,000+ vessels across 75 countries, delivering 25% cost savings. In another engagement the team converted a US mortgage enterprise’s loan system from PL/SQL to microservices, achieving 30% faster processing and reducing data errors by 40%.

Partnering with the Right Legacy Modernization Service Provider

A successful legacy modernization approach balances business objectives, technical complexity, and organizational readiness.

• Align Scope and Provider Capability
  Large, multiyear programs often benefit from a global systems integrator. Focused refactoring or design-led initiatives may be better served by engineering specialists or boutique consultancies.
• Evaluate Automation Tooling
  Request demonstrations of AI-based code analyzers, migration dashboards, and automated test suites. Mature tooling can compress migration timelines and reduce defect rates.
• Assess Change Management Maturity
  Successful modernization extends beyond code. Ensure prospective partners offer comprehensive training, communications planning, and key performance indicator frameworks that connect technical outputs to business outcomes.
• Insist on Phased Value Delivery
  Adopt a roadmap that delivers incremental benefits—cost reduction, performance gains, or new digital capabilities—each quarter, maintaining executive support and mitigating risk.

By carefully evaluating potential partners against these criteria, organizations can ensure a successful modernization journey that aligns with their strategic objectives.

Addressing the Common Challenges in Legacy Modernization

Legacy application modernization initiatives falter when critical disciplines are overlooked.

• Equating Lift-and-Shift with Full Modernization– Rehosting can provide short-term relief but rarely delivers long-term agility. Plan subsequent replatform or refactor phases.
• Underestimating User Adoption Effort– Allocate budget for user experience improvements, training, and governance to ensure sustained adoption.
• Focusing Exclusively on Cost Reduction– Track additional metrics such as release velocity, incident frequency, and customer experience scores to capture the full value of modernization.

Legacy Modernization Services That Enable ROI in 2025 and Beyond

Technical debt behaves much like accumulating interest—the longer it remains unaddressed, the greater the future liability. Whether the initial step is an API wrapper or a full rebuild, the objective remains constant: reduce risk, optimize cost, and enable continuous innovation. Begin with a targeted pilot, verify outcomes, and expand in controlled phases.

For organizations seeking external expertise, the ten application modernization companies profiled here represent proven choices, each with distinct strengths. The optimal moment to modernize is today; the sooner technical debt is converted into strategic capability, the sooner the enterprise can capitalize on new opportunities.

Ready to rethink legacy systems? Let’s explore the possibilities together.