The accumulation of supply chain lead time caused by inventory handling inside the warehouse, which includes waiting time, queue time, and unexpected delays, makes it difficult to fulfill demand shocks and third-party stakeholder needs. Regardless of how complex production planning is, these issues persist and change. In that instance, studying or mapping a pharmaceutical warehouse supply chain inventory would be a significant difficulty in identifying areas for future development. The study focused on the warehouse of a pharmaceutical firm. Following extensive fieldwork and literature gap analysis, a case study technique was determined to be the most appropriate methodology for this study.  Lean unified simulation modeling leverages Supply Chain Value Stream Mapping (SCVSM) and Discrete Event Simulation (DES) to capture, record, evaluate, and decrease inventory waiting times, delays, queues, and other wastes for a specific product family. Following various lean proposals in the future state SCVSM, the findings of this investigation reveal a significant improvement in warehouse lead time. There was significant increase in the value-added time and reduction in non-value added time with the assistance of risk free DES models that replicated the entire operations for the purpose of present and future state simulation along with suggestions for improvements. This study proved to possess strong managerial and practical implications that shall help in better decision-making by deeply understanding the supply chain activities that occur as discrete events inside a warehouse.