Background Few studies have evaluated the effect of Emergency Department (ED) overcrowding on resident education. Objectives To determine the impact of ED overcrowding on Emergency Medicine (EM) resident education. Materials and Methods A prospective cross-sectional study was performed from March to May 2009. Second- and third-year EM residents, blinded to the research objective, completed a questionnaire at the end of each shift. Residents were asked to evaluate the educational quality of each shift using a 10-point Likert scale. Number of patients seen and procedures completed were recorded. Responses were divided into ED overcrowding (group O) and non-ED overcrowding (group N) groups. ED overcrowding was defined as >2 h of ambulance diversion per shift. Questionnaire responses were compared using Mann–Whitney U tests. Number of patients and procedures were compared using unpaired T-tests. Results During the study period, 125 questionnaires were completed; 54 in group O and 71 in group N. For group O, the median educational value score was 8 (interquartile range [IQR] 7–10), compared to 8 (IQR 8–10) for group N ( p = 0.24). Mean number of patients seen in group O was 12.3 (95% confidence interval [CI] 11.4–13.2), compared to 13.9 (95% CI 12.7–15) in group N ( p = 0.034). In group O, mean number of procedures was 0.9 (95% CI 0.6–1.2), compared to 1.3 (95% CI 1–1.6) in group N ( p = 0.047). Conclusions During overcrowding, EM residents saw fewer patients and performed fewer procedures. However, there was no significant difference in resident perception of educational value during times of overcrowding vs. non-overcrowding.