The objective of this study is to improve the efficiency of emergency departments (ED) by decreasing the overcrowding and patient waiting times. A hybrid methodology composed of a combination of lean techniques and discrete event simulation models was followed. Value stream mapping (VSM) was used as a lean technique with the aid of the ED staff. After obtaining the future state map of the ED, two discrete event simulation models were developed. By reviewing each triage process, the suggestions and proposed changes were incorporated into the future state map. There were five active process changes, each reducing lead and value added times by different amount. The usage of lean techniques can effectively reduce patient lead and value added times inside the ED, and when combined with discrete event simulation modeling, possible outcomes of the lean techniques can be tested and verified. This study contributed to the potential of lean techniques combined with simulation models in the case of reducing ED overcrowding and patient waiting times.