BACKGROUND: Adoption of residents' working time restrictions potentially undermines surgical training by reduction of operating room exposure. Simulation has been proposed as a way to acquire necessary skills in a laboratory environment but remains difficult to incorporate into training schedules. This study assessed whether residents working successive nights could acquire endovascular skills similar to colleagues working day shifts. METHODS: This prospective observational cohort study recruited 20 junior residents, divided into day shift and night shift groups by their respective call schedule. After initial cognitive skills training, a validated renal artery stent module on an endovascular simulator was completed over a series of seven sequential shifts during 1 week. The primary outcome measure was serial technical skill assessments. Secondary measures comprised assessments of activity, cognitive performance, introspective fatigue, quality, and quantity of preceding sleep. RESULTS: Both groups demonstrated significant learning curves for total time at the first session median vs seventh session median (181 vs 564 seconds [P < .001]; night, 1399 vs 572 [P < .001]), fluoroscopy time (day, 702 vs 308 seconds, [P < .001]; night, 669 vs 313 [P < .001]), and contrast volume (day, 29 vs 13 mL [P < .001]; night, 40 vs 16 [P < .001]). Residents working day shifts reached plateau 1 day earlier in the above measures vs those on night duty. The night shift group walked more steps (P < .001), reviewed more patients (P < .001), performed worse on all cognitive assessments (P < .05), slept less (P < .05), had poorer quality of sleep (P = .001), and was more fatigued (P < .001) than the day shift group. Acquired skill was retained a week after completion of shifts. CONCLUSION: Technical skills training after night shift work enables acquisition of endovascular technical skills, although it takes longer than after day shift training. This study provides evidence for program directors to organize simulation-based training schedules for residents on night shift rotations.