This study aims at proposing a method that combines value stream mapping (VSM) and Monte Carlo simulation for identifying improvement opportunities in the flow of value, taking into account the inherent variability of the uncertainty sources. A cross-functional team was involved to draw the current and future state maps. Moreover, leaders were interviewed to define the most critical uncertainty sources of the value stream, whose variability was verified through a thirty-day in loco data collection in a university-hospital. These variability data were inputted into the simulation model in order to comprehend how the uncertainty sources impact lead time. Findings show that the proposed approach allows the identification of opportunities for improvement that are not taken into consideration in traditional application of the VSM, providing a more realistic condition of the current state.