Productivity helps manufacturing companies compete or remain competitive in global markets. Manufacturing companies are striving to compete in the global markets to remain profitable and increase its productivity. Lean manufacturing technique has been designed to identify and eliminate waste used to improve productivity. This study aims to improve the productivity of a door and window manufacturing plant using lean manufacturing and simulation modelling.  This study applies lean tools to a door and window manufacturing plant to identify and eliminate waste from the system. The impact of lean application is then analyzed using simulation modelling, and a new model of the system is proposed. The integration of lean manufacturing and simulation modelling was found to improve productivity in this manufacturing plant. The results illustrated an increase in throughput and an improvement in the company's overall productivity.