Background: Following ST-segment elevation myocardial infarction (STEMI), patients with cardiac dysfunction have limitations in performing physical activity. Right ventricular (RV) function is a determinant in improving functional capacity, and cardiac rehabilitation (CR) is essential for this patient cohort., Objective: To evaluate the association of RV function with exercise tolerance after a CR program in patients with STEMI., Methods: Retrospective cohort study in patients with STEMI from January to December 2019. They underwent an echocardiographic assessment of RV function before a 16-session CR program. A cardiopulmonary exercise (CPX) testing was performed before and after the CR program. We analyzed whether RV function measured before CR was significantly associated with exercise tolerance before and after the CR program and the degree of improvement. Comorbidity, demographic and anatomic variables were documented. A p-value < 0.05 was considered statistically significant., Results: A total of 109 patients were included. Of all, 3.7% had global RV dysfunction, 10.1% had radial RV dysfunction, and 11% had longitudinal RV dysfunction. An association between radial or longitudinal RV dysfunction and the absence of improvement in cardiorespiratory fitness (> 1 peak VO2equivalents) was observed (p = 0.028, p = 0.008, respectively). A significant correlation was observed between longitudinal RV dysfunction with initial peak VO2equivalents (pVO2eq) (p = 0.046), final pVO2eq (p = 0.003), and difference in pVO2eq (p = 0.009). A correlation was also identified between global RV dysfunction and the initial pVO2eq (p = 0.045), final pVO2eq (p = 0.012), and difference in pVO2eq (p = 0.032)., Conclusions: RV dysfunction is associated with a lower capacity to exercise; CR programs can be extended or modified in these patients.