Objective: In this study Sophora pachycarpa C.A. Mey. is a plant from the family of Fabaceae. Here, we investigated the antitumor effect various fractions of a methanol extract of S. pachycarpa on different cancer cell lines including A549, HeLa, MCF-7, PC3, L929 and Human umbilical cord Leukocytes. Meanwhile the role of apoptosis was explored in this toxicity. Materials and Methods: Malignant and non-malignant cells were cultured in RPMI 1640 medium and incubated with different concentrations of plant extracts. Cell viability was quantitated by MTT assay. Apoptotic cells were determined using PI staining of DNA fragmentation by flow cytometry (sub-G1 peak). Results: S. pachycarpa inhibited the growth of malignant cells in a dose-dependent manner. Among solvent fractions of Sophora pachycarpa, the methylene chloride fraction was found to be more toxic compared to other fractions. S. pachycarpa -induced a sub-G1 peak in flow cytometry histogram of treated cells compared to control indicating apoptotic cell death is involved in S. pachycarpa -induced toxicity. Conclusion: S. pachycarpa exerts cytotoxic effects in different cancer cell lines in which apoptosis plays an important role. Thus S. pachycarpa could be considered as a potential chemotherapeutic agent in cancer treatment.