Objective: Cardiac surgeons experience unpredictable overnight operative responsibilities, with variable rest before same-day, fi rst-start scheduled cases. This study evaluated the frequency and associated impact of a surgeon's ' s overnight operative workload on the outcomes of their same-day, fi rst-start operations. Methods: A statewide cardiac surgery quality database was queried for adult cardiac surgical operations between July 1, 2011, and March 1, 2021. Nonemergency, fi rst-start, Society of Thoracic Surgeons predicted risk of mortality operations were stratified fi ed by whether or not the surgeon performed an overnight operation that ended after midnight. A generalized mixed effect model was used to evaluate the effect of overnight operations on a Society of Thoracic Surgeons composite outcome (5 major morbidities or operative mortality) of the fi rst-start operation. Results: Of all fi rst-start operations, 0.4% % (239/56,272) had a preceding operation ending after midnight. The Society of Thoracic Surgeons predicted risk of morbidity and mortality was similar for fi rst-start operations whether preceded by an overnight operation or not (overnight operation: 11.3%; % ; no overnight operation: 11.7%, % , P = .42). Unadjusted rates of the primary outcome were not significantly fi cantly different after an overnight operation (overnight operation: 13.4%; % ; no overnight operation: 12.3%, % , P = .59). After adjustment, overnight operations did not signifi- fi- cantly impact the risk of major morbidity or mortality for fi rst-start operations (adjusted odds ratio, 1.1, P = .70). Conclusions: First-start cardiac operations performed after an overnight operation represent a small subset of all fi rst-start Society of Thoracic Surgeons predicted risk operations. Overnight operations do not significantly fi cantly influence fl uence the risk of major morbidity or mortality of fi rst-start operations, which suggests that surgeons exercise proper judgment in determining appropriate workloads. (JTCVS Open 2024;20:101-11)