Objective: To evaluate the cytotoxic activities of Premna odorata (P. odorata) leaves and bark, Artocarpus camansi (A. camansi) and Gliricidia sepium against selected human cancer cell lines by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Methods: The crude extracts of P. odorata, A. camansi and Gliricidia sepium were subjected to liquid–liquid partitioning by using hexane and ethyl acetate to separate compounds based on their polarity. The fractions were tested for their cytotoxic activity against human colon cancer cell line (HCT116), breast cancer cell line (MCF-7), lung adenocarcinoma cell line (A549) and Chinese hamster ovary cell line (AA8) by using MTT assay. Results: Based on the standard values of toxicity set by the study of Suffness and Pezzuto, P. odorata leaves and P. odorata bark hexane fractions and A. camansi leaves were all considered highly cytotoxic against the selected human cancer cell lines. P. odorata bark hexane extract exhibited the highest selectivity index for HCT116, MCF-7 and A549 cancer cell lines. Conclusions: The results obtained indicated that P. odorata leaves and bark and A. camansi leaves have excellent cytotoxic activity and warrant further studies to isolate novel compounds for chemotherapeutic use.