To assess whether the quality of chest compressions (CC) differs before and after a night shift. We carried out a cluster randomized study in three Emergency Departments and three ICUs in Paris, France. Physicians were assessed on a control day and immediately following after a night shift. The primary endpoint was the proportion of CC with a depth greater than 50 mm. We analyzed 67 participants. The proportion of CC with a depth greater than 50 mm was similar on a control day and after a night shift [52% in both groups, mean difference of 0 (95% confidence interval: -17 to 17)]. Other indicators of CC quality were unchanged after a night shift, except for the mean depth of CC (51 vs. 48 mm, P=0.01). We report in our sample that the quality of CC after a night shift is not inferior to a control day.