Despite the use of numerous new and advanced technologies in construction projects, the industry’s efficiency remains low. This business has faced significant challenges for a long time, such as non-value-added activities, also known as waste. Lean construction (L.C.) is one method for improving the situation by reducing waste and increasing value for the client. This study provides an in-depth literature review to provide a comprehensive list of all critical drivers and groups all these drivers into one research paper in order to determine the importance (weights) of these drivers and their relative importance, and to propose an innovative methodology for ranking them using Simos’ approach. Seven construction project case studies were proposed. Their lean status was assessed, the key-list was verified using a Weighted-Sum Model as a multi-criteria decision-making technique to rank them, the best one in terms of lean implementation was found. Subsequently, a sensitivity analysis was conducted to determine the most critical criterion for the key list. The following are some of the study’s main findings: 18 key drivers were identified and ranked, a clear definition of the client’s requirements was the most global weight between factors, and the case studies demonstrated that more than 60% of the lean drivers are implemented in Egypt. Day-to-day observation and standardized work were the top two most widely used lean practices in Egypt.