Current practice and method of the Ethiopian building construction industry is relatively traditional; which is observed through its low productivity, poor workmanship, high wastage and lack of quality work to list a few. Even though there are many research has conducted to address the challenge in improving the construction method, there is still a gap in improving minimization of physical and non-physical waste through modern construction approaches. The objective of this study is to assess the implementation of lean construction techniques in reducing waste and improve performance of building construction projects in the city of Bahir Dar, Ethiopia. The concept of lean thinking in construction project is designed to reduce waste, improve communication and promote teamwork and integration through a common set of tools and techniques. This paper determine cause of waste, identifies and categorizes waste, to find remedial actions. In addition to this implementation barrier of lean construction approach also assessed to overcome problem, facilitate project progress. Finally, recommendation also offered for better public construction process. To address successful implementation of lean approach qualitative and quantitative research methods were applied and perception of adopting new philosophies like lean approach were analyzed. Cause of waste associated with flow, management activity, change or conversion were categorized as controllable and uncontrollable or (external causes), wastes were also categorized based on the judgment of the construction professionals‟ experience. From the results of expert‟s ideas unqualified workforce, poor information quality, lack of waste management plan, poor execution of work, lack of supervision and weather condition are fundamental causes of wastes. Determine what must be done before execution of work assignment, inspection and enforcement allocating and leveling of resource and perform team integration are some of the potential solution of waste reduction. The results from experts were correlated and discussed with the data gathered qualitatively. A conceptual framework for implementing lean construction approach is also incorporated in this thesis. Finally, conclusion and recommendation were drawn based on the collected and analyzed data on waste reduction through lean approach.