Objective: The aim of this study is to evaluate the preventive effects of carvedilol on doxorubicin-induced cardiotoxicity. Methods: In this trial, 70 female patients with breast cancer who were candidates to receive doxorubicin were enrolled, from which 30 were selected randomly to receive carvedilol 6.25 mg daily during chemotherapy, with the rest receiving placebo as the control group. Both groups were evaluated 1 week before and 1 week after chemotherapy by measuring the left ventricular ejection fraction and strain/strain rate. Results: Data analysis showed that the case group presented no significant reduction in strain and strain-rate parameters after intervention, while there was a significant reduction in these parameters in the control group (all p values <0.001). Also, the mean differences of strain parameters in the case group were significantly less than in the control group in all evaluated heart walls (basal septal strain, p = 0.005, basal lateral strain, p = 0.001, basal inferior strain, p < 0.001, and basal anterior strain, p < 0.001); the same was true for the strain-rate parameters (the p values for basal septal, basal lateral, basal inferior and basal anterior strain rate were 0.037, 0.037, 0.002 and <0.001, respectively). Conclusion: This study shows that carvedilol can prevent doxorubicin-induced cardiotoxicity. Whether this prophylaxis should be considered as the preferred method needs further investigation.