Ovarian cancer is one of the cause of death from gynaecological complications. Many female patients are often diagnosed with various stages of the disease. Treatment has proven very difficult due to metastasis resulting in multiple infections. The leaves of Annona muricata were extracted and then fractionated by column chromatography. In vitro cytotoxicity tests were performed with fractions and with an isolated compound on ovarian cancer cell line, at concentrations of 6.25-200 μg/mL for crude extract and pure compound. Cytotoxicity was measured after 24, 48 and 72 hours using MTT assay. In vivo cytotoxicity was tested on ascites, developed in the abdomen of albino mice after inoculation with human epithelia OV7-CDNA20μL cells intraperitoneally. Cytotoxicity of the crude extract and pure compound for the cell line at all concentrations was greater than 10 μg/mL, at 48 hours (p≤0.05; ANOVA). Both the crude plant extract as well as the pure compound of A. muricata leaf killed the cancer cell at a final concentration of 200 μg/mL and 100μg/ mL respectively at all concentrations. Mean survival time (MST) and percentage increase in life span were highest in group IV with values 3.0 ± 0 .03 and 5±0.05 respectively at 1000 mg / kg body weight (b.w).Packed cell volume (PCV) and Non-viable tumors cell counts (NVC) showed progressive increase as the dosage increased from 10 -1000 mg/kg in all the groups while viable tumor cell counts decreased in all the groups as compared to doxorubicin. The study showed that A. muricata leaf has potent anti-ovarian cancer effects against ovarian cancer cell line, and represents a source for ovarian cancer therapy.