Background: Stroke simulation-based training has been associated with improved stroke quality metrics. The purpose of this study was to assess whether high-fidelity acute stroke simulation participation led to better knowledge retention one month post simulation in off-service residents. Methods: Off-service residents were provided with non-mandatory pre-simulation pre-reading on stroke. Immediately before stroke simulation, they completed a questionnaire to test their knowledge on a set of 8 questions related to stroke. Immediately post-stroke simulation, they were provided with a debrief including teaching on stroke. After the debrief and one month later, they completed the same questionnaire again. Results: There were a total of 16 off-service resident participants. Wilcoxon signed ranks test was performed. There was a significant difference between pre-simulation and immediate post-simulation scores on the knowledge retention questionnaire (p = 0.008). There was a significant difference between pre-simulation and one-month post-simulation on the knowledge retention questionnaire (p = 0.007). There was no difference between immediate post-simulation and one-month post-simulation on the knowledge retention questionnaire (p = 0.77). Conclusions: Participants performed better on the questionnaire after the simulation, and this improved performance was retained at one month. This is the first study to demonstrate delayed knowledge retention in stroke simulation literature.