Business transformation is increasingly a key driver for many organizations in today’s competitive environment where the focus is either on cost reduction by means of improving operational efficiency or on increasing the market share through innovation and other means of growth. Information Technology (IT) is looked upon as one of the key enablers for business innovation and competitive differentiation. As a result, many organizations identify a number of IT initiatives that enable business transformation and alignment of IT to business objectives and drivers. Such initiatives are often undertaken as part of large, multi-year business transformation programs that are aimed at changing and optimizing business processes and enhancing the IT capabilities that enable them. The initial effort and excitement of such changes often propel many transformational projects directly into an execution phase where focus is often on delivery without appropriate investments in program planning and further in planning and definition of the enterprise architecture. Such an approach often results in lack of appropriate guidance for the implementation projects and leads to large pitfalls. Organizations become unclear of what to deliver and how to deliver the change that can provide value to business and provide a return on the investment. Eventually this lack of planning leads to a failure to achieve the transformational objectives. This article highlights the need for enterprise architecture definition in large transformation programs, key considerations for defining the enterprise architecture, key challenges involved, and concludes with the benefits enterprise architecture brings to various stakeholders involved in transformation programs.