IMPORTANCE: Patients with acute coronary syndrome (ACS) and elevated depressive symptoms are at increased risk for recurrent cardiovascular events and mortality, worse quality of life, and higher health care costs. These observational findings prompted multiple scientific panels to advise universal depression screening in survivors of ACS prior to evidence from randomized screening trials. OBJECTIVE: To determine whether systematically screening for depression in survivors of ACS improves quality of life and depression compared with usual care. DESIGN, SETTING, AND PARTICIPANTS: A 3-group multisite randomized trial enrolled 1500 patients with ACS from 4 health care systems between November 1, 2013, and March 31, 2017, with follow-up ending July 31, 2018. Patients were eligible if they had been hospitalized for ACS in the previous 2 to 12 months and had no prior history of depression. All analyses were performed on an intention-to-treat basis. INTERVENTIONS: Patients with ACS were randomly assigned 1:1:1 to receive (1) systematic depression screening using the 8-item Patient Health Questionnaire, with notification of primary care clinicians and provision of centralized, patient-preference, stepped depression care for those with positive screening results (8-item Patient Health Questionnaire score ≥10; screen, notify, and treat, n = 499); (2) systematic depression screening, with notification of primary care clinicians for those with positive screening results (screen and notify, n = 501); and (3) usual care (no screening, n = 500). MAIN OUTCOMES AND MEASURES: The primary outcome was change in quality-adjusted life-years. The secondary outcome was depression-free days. Adverse effects and mortality were assessed by patient interview and hospital records. RESULTS: A total of 1500 patients (424 women and 1076 men; mean [SD] age, 65.9 [11.5] years) were randomized in the 18-month trial. Only 71 of 1000 eligible survivors of ACS (7.1%) had elevated 8-item Patient Health Questionnaire scores indicating depressive symptoms at screening. There were no differences in mean (SD) change in quality-adjusted life-years (screen, notify and treat, -0.06 [0.20]; screen and notify, -0.06 [0.20]; no screen, -0.06 [0.18]; P = .98) or cumulative mean (SD) depression-free days (screen, notify and treat, 343.1 [179.0] days; screen and notify, 351.3 [175.0] days; no screen, 339.0 [176.6] days; P = .63). Harms including death, bleeding, or sleep difficulties did not differ among groups. CONCLUSIONS AND RELEVANCE: In patients with ACS without a history of depression, systematic depression screening with or without providing depression treatment did not alter quality-adjusted life-years, depression-free days, or harms. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01993017.