Abstract ------------- Background ---------------- Like other businesses, the failures and problems faced by the software development industry over the time have motivated experts to look for software process improvement to create quality software rapidly, repeatedly, and reliably. Objective ------------ The purpose of this study is to evaluate if and how Lean thinking and principles primarily associated with auto manufacturing industry can be applied to software development lifecycle for Software Process Improvement (SPI). The secondary aim is to analyze how BPR can be integrated with Lean software development for process improvement. Method ---------- A derived Lean-BPR adoption pattern model is used as a theoretical framework for this thesis. The seven Lean software development principles along with four-step BPR process are selected as process improvement patterns, which effects the KPIs of a software organization. This research study incorporates both Qualitative and Quantitative methods and data to analyze the objectives of this study. The methodological framework of Plan-Do-Check-Act is used in the case study to implement process re-engineering incorporating Lean and BPR principles. The impact of adopting the Lean and BPR principles is assessed in terms of cost, productivity, quality of products and resource management. Results ---------- Application of Lean and BPR principles for software process improvement in the organization under study resulted in 79% improvement in test coverage, 60% reduction in time for test execution and analysis and 44% reduction in cost for fixing defects that were being passed to customer in past. Conclusion ------------- Based on case study results, it can be concluded that Lean, a bottom up approach, characterized by empowerment of employees to analyze and improve their own working process can be effectively combined with IT centric traditionally top down BPR approach for improving KPI’s and software processes.