Purpose - The purpose of this article is to present a unified model by combining lean and CMMI-SVC best practices. The model would be very useful for CMMI-SVC organizations that plan to implement lean best practices. Design/methodology/approach - The paper is based on the review of the contemporary literature on lean concepts and the CMMI-SVC v1.3 model, including books, journal articles and handbooks. A group of practitioners and experts with theoretical and practical expertise on the CMMI framework, software process improvements as well as lean principles and services were involved to find out which lean principles are applicable to service organization and also the compatibility of lean and CMMI-SVC v1.3 practices. Findings - The authors have presented a unified model by combining CMMI-SVC v1.3 and lean best practices which can be applied to service organizations. In the future they would like to implement their unified model within IT service organizations to check its feasibility and effectiveness in real world. It would also provide an opportunity to explore the strengths and weaknesses of the unified model, based on which it can be further refined and matured. Originality/value - The model has been designed in such a way that lean practices can be plugged-in to CMMI-SVC model process areas. By including lean practices to CMMI-SVC model, the process improvement initiatives will be aligned with the business objectives. The unified model will be useful to the organizations that would like to implement lean concepts within the CMMI-SVC framework.