Participation in cardiac rehabilitation is associated with significant decreases in morbidity and mortality. Despite the proven benefits, cardiac rehabilitation is severely underutilized in certain populations, specifically those with lower socioeconomic status (SES). To assess the efficacy of early case management and/or financial incentives for increasing cardiac rehabilitation adherence among patients with lower SES. This randomized clinical trial enrolled patients from December 2018 to December 2022. Participants were followed up for 1 year with assessors and cardiac rehabilitation staff blinded to study condition. Patients with lower SES with a cardiac rehabilitation-qualifying diagnosis (myocardial infarction, coronary artery bypass graft, percutaneous coronary intervention, heart valve replacement/repair, or stable systolic heart failure) were recruited. Then patients attended one of 3 cardiac rehabilitation programs at 1 university or 2 community-based hospitals. A consecutively recruited sample was randomized and stratified by age (<57 vs ≥57 years) and smoking status (current smoker vs nonsmoker or former smoker). Participants were randomized 2:3:3:3 to either a usual care control, case management starting in-hospital, financial incentives for completing cardiac rehabilitation sessions, or both interventions (case management plus financial incentives). Interventions were in place for 4 months following informed consent. The main outcome was cardiac rehabilitation adherence (proportion of patients completing ≥30 sessions). The a priori hypothesis was that interventions would improve adherence, with the combined intervention performing best. Of 314 individuals approached, 11 were ineligible, and 94 declined participation. Of the 209 individuals who were randomized, 17 were withdrawn. A total of 192 individuals (67 [35%] female; mean [SD] age, 58 [11] years) were included in the analysis. Interventions significantly improved cardiac rehabilitation adherence with 4 of 36 (11%), 13 of 51 (25%), 22 of 53 (42%), and 32 of 52 (62%) participants completing at least 30 sessions in the usual care, case management, financial incentives, and case management plus financial incentives conditions, respectively. The financial incentives and case management plus financial incentives conditions significantly improved cardiac rehabilitation adherence vs usual care (adjusted odds ratio [AOR], 5.1 [95% CI, 1.5-16.7]; P = .01; AOR, 13.2 [95% CI, 4.0-43.5]; P < .001, respectively), and the case management plus financial incentives condition was superior to both case management or financial incentives alone (AOR, 5.0 [95% CI, 2.1-11.9]; P < .001; AOR, 2.6 [95% CI, 1.2-5.9]; P = .02, respectively). Interventions were received well by participants: 86 of 105 (82%) in the financial incentives conditions earned at least some incentives, and 96 of 103 participants (93%) assigned to a case manager completed the initial needs assessment. In this randomized clinical trial, financial incentives improved cardiac rehabilitation adherence in a population with higher risk and lower SES with additional benefit from adding case management. ClinicalTrials.gov Identifier: NCT03759873.