Anthocyanin is a natural plant pigment and potent antioxidant. This study was designed to investigate the effects of anthocyanin extracted from black soybeans on a rat model of benign prostatic hyperplasia (BPH), a disease associated with the geriatric population. Thirty male rats were divided into five experimental groups: a control group, a BPH-induced group, and three BPH-induced groups that received oral doses of anthocyanin (40, 80, and 160 mg/kg). Prostate hyperplasia was induced by the administration of testosterone propionate for 4 weeks. Following BPH induction, the anthocyanin-treated groups received the compound for 4 weeks. After anthocyanin treatment, the prostates from the rats in all groups were removed, weighed, and subjected to histological examination. Apoptosis in the prostates was measured by the TUNEL assay. The mean prostate weight for the control animals was 674.17 ± 28.24 mg, whereas the BPH-induced rats had a mean prostate weight of 1098.33 ± 131.31 mg. The mean prostate weights for the rats receiving 40, 80, and 160 mg/kg anthocyanin were 323.00 ± 22.41, 324.00 ± 26.80, and 617.50 ± 31.08 mg, respectively. The average prostate weight in the BPH-induced group was significantly higher than in the control group (p < 0.05), whereas the prostate weights in the anthocyanin-administered groups were significantly lower than in the BPH-induced group (p < 0.05). Injected testosterone led to prostatic hyperplasia as observed histologically, but anthocyanin administration helped to prevent this change. Apoptotic body counts were significantly higher in groups receiving anthocyanin than in the BPH-induced group (p < 0.05). These results suggest that anthocyanin may be effective in decreasing the volume and suppressing the proliferation of the prostate. Further studies are needed to better understand the mechanisms and actions of anthocyanin, and these studies may lead to the clinical application of anthocyanin in treating BPH.