Background Complete revascularization reduces cardiovascular events in patients with acute coronary syndromes (ACSs) and multivessel disease. The optimal time point of non–target‐vessel percutaneous coronary intervention (PCI) remains a matter of debate. The aim of this study was to investigate the impact of early (<4 weeks) versus late (≥4 weeks) staged PCI of non–target‐vessels in patients with ACS scheduled for staged PCI after hospital discharge. Methods and Results All patients with ACS undergoing planned staged PCI from 2009 to 2017 at Bern University Hospital, Switzerland, were analyzed. Patients with cardiogenic shock, in‐hospital staged PCI, staged cardiac surgery, and multiple staged PCIs were excluded. The primary end point was all‐cause death, recurrent myocardial infarction and urgent premature non–target‐vessel PCI. Of 8657 patients with ACS, staged revascularization was planned in 1764 patients, of whom 1432 patients fulfilled the eligibility criteria. At 1 year, there were no significant differences in the crude or adjusted rates of the primary end point (7.8% early versus 10.8% late, hazard ratio [HR], 0.72 [95% CI, 0.47–1.10], P =0.129; adjusted HR, 0.80 [95% CI, 0.50–1.28], P =0.346) and its individual components (all‐cause death: 1.5% versus 2.9%, HR, 0.52 [95% CI, 0.20–1.33], P =0.170; adjusted HR, 0.62 [95% CI, 0.23–1.67], P =0.343; recurrent myocardial infarction: 4.2% versus 4.4%, HR, 0.97 [95% CI, 0.475–1.10], P =0.924; adjusted HR, 1.03 [95% CI, 0.53–2.01], P =0.935; non–target‐vessel PCI, 3.9% versus 5.7%, HR, 0.97 [95% CI, 0.53–1.80], P =0.928; adjusted HR, 1.19 [95% CI, 0.61–2.34], P =0.609). Conclusions In this single‐center cohort study of patients with ACS scheduled to undergo staged PCI after hospital discharge, early (<4 weeks) versus late (≥4 weeks) staged PCI was associated with a similar rate of major adverse cardiac events at 1 year follow‐up. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02241291.