Construction projects in developing countries face challenges related to inefficient practices and high levels of waste, leading to cost overruns and delays. Lean Construction (LC) principles are an approach to minimize waste and improve efficiency in construction projects. However, the impact of adopting LC on waste reduction in developing country contexts remains a subject that requires investigation. The current case study aimed to examine how implementing LC. principles can reduce waste in building projects in developing nations. The research utilizes a mixed-method approach; Qualitative interviews are conducted with stakeholders, including project managers, contractors, and architects, to gather their perceptions of the most common waste type in the construction process and how the lean principles implementation minimizes waste. Quantitative approach: a case study was conducted using a lean simulation model by ARENA software, to measure the impact of LC. principles on the overall performance of the construction (reinforcement process). Our Results showed that the lean model enhances the process efficiency by eliminating non-value-added activities, standardizing work procedures, and fostering continuous improvement. These practices lead to a reduction in wasted resources, such as the reinforcement process (improvement in overall cutting process by 67.1% and bending process by 21%) and enhance work productivity by 19.6%, and thus refinement in the overall time cycle by 24.5%. In summary, by adopting lean principles, businesses can create a more sustainable and efficient future while contributing to preserving natural resources and focusing on value-added processes.