Methanolic extract of Cynometra cauliflora whole fruit was assayed for cytotoxicity against the human promyelocytic leukemia HL-60 and the normal mouse fibroblast NIH/3T3 cell lines by using the MTT assay. The CD50 of the extract for 72 hours was 0.9 μg/mL whereas the value for the cytotoxic drug vincristine was 0.2 μg/mL. The viability of the NIH/3T3 cells was at 80.0% when treated at 15.0 μg/mL. The extract inhibited HL-60 cell proliferation with dose dependence. AO/PI staining of HL-60 cells treated with the extract revealed that majority of cells were in the apoptotic cell death mode. Flow cytometry analysis of HL-60 cells treated at CD50 of the extract showed that the early apoptotic cells were 31.0, 26.3 and 19.9% at 24, 48, and 72 hours treatment, respectively. The percentage of late apoptotic cells was increased from 62.0 at 24 hours to 64.1 and 70.2 at 48 and 72 hours, respectively. Meanwhile, percent of necrotic cells were 4.9, 6.6, and 8.5 at 24, 48, and 72 hours, respectively. This study has shown that the methanolic extract of C. cauliflora whole fruit was cytotoxic towards HL-60 cells and induced the cells into apoptotic cell death mode, but less cytotoxic towards NIH/3T3 cells.