Abstract: Objective To investigate the improvement effect of finasteride on cardiac function in male obese rats, and analyze its mechanism. Methods Male SD rats were selected as the study subjects from May 2023 to May 2025. Those fed with normal diet were assigned to the normal control group (NC group), and those fed with high-fat diet to establish obesity models were assigned to the highfat experimental group (HF group). After successful modeling, rats in the HF group were randomly divided into the high-fat control group (HC group) and the finasteride group. Rats in the finasteride group received finasteride by gavage at 5 mg·kg^-1·d^-1, while rats in the NC group and HC group were given equal volume normal saline by gavage. The intervention lasted for 14 consecutive days. Basic morphological indicators of rats were observed, and cardiac function was evaluated, and the relative mRNA expression of 5α-reductase 2 (5α-R2) was detected by semi quantitative reverse transcription polymerase chain reaction (RT-PCR); the level of dihydrotestosterone (DHT) was measured by enzyme-linked immunosorbent assay (ELISA); the levels of myocardial oxidative stress indicators were detected by Western blot (WB), and the levels of mitochondrial function indicators were measured by ELISA. Results After intervention, body weight, Lee's obesity index and visceral adipose tissue mass in finasteride group and HC group were higher than those in NC group (P < 0.05); body weight in finasteride group was higher than that in HC group (P < 0.05). After intervention, left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS), left ventricular end-systolic diameter (LVESD), heart mass, protein level of glutathione peroxidase 4 (GPX4) and mitochondrial glutathione peroxidase (GSH-Px) level in finasteride group were higher than those in HC group. While left ventricular posterior wall systolic thickness (LVPWs), low-frequency/high-frequency ratio (LF/ HF), mRNA expression of 5α-R2 in prostate tissue, serum dihydrotestosterone (DHT) level, protein level of 4-hydroxynonenal (4-HNE) and mitochondrial malondialdehyde (MDA) level were lower than those in HC group (P < 0.05). Conclusion Finasteride can improve cardiac function in male obese rats, and its mechanism may be related to inhibiting 5α-R2 expression, reducing DHT levels, alleviating myocardial oxidative stress and protecting mitochondrial function.