Soursop leaves contain annonaceous acetogenins active compounds that have a cytotoxic effect on cancer cells. The aim of this study is to determine the effect of soursop leaf extract on the viability and inhibitory rate on the prostate cancer cell line PC3. The study was an experimental in vitro study. Subjects were 5 groups of PC3 cell line: cell control group, the group treated with methanol extract of soursop leaves (EMDS) with the concentrations of 6.25; 12.5 and 25 mg/mL and the doxorubicin group. The groups were tested using the MTT cell viability assay at 0 and 24 hours of incubation followed by PC3 cell morphology examination. Data were analyzed by ANOVA test. The results showed a decrease in the OD value of 6.25 and 12.5 ug/mL EMDS group, but statistical tests did not differ significantly and the EMDS 12.5 mg/mL group showed the highest ability in inhibiting cell viability (OD 0.94). Observation of cell morphology showed cytotoxic effects. Conclusion: The methanol extract of soursop leaf has a potential as an anticancer against prostate cancer cell lines despite the very small inhibitory effect.