Concanavalin a lectin from seeds of Canavalia spp. is extracted and purified to study antitumor effect in vitro. Canavalia ensiformis and Canavalia gladiata were tested for their cytotoxicity, apoptotic potential and effect on cell cycle phases in HT-29 colon carcinoma cells. It was revealed that both lectins inhibit growth of HT-29 cells in dose dependent manner without affecting normal Human embryonic kidney 293T cells. The half maximal inhibitory concentration values were 14.86 and 10.45 μg/ml for Canavalia ensiformis and Canavalia gladiata respectively. Both lectins induced apoptotic morphology like chromatin condensation, deoxyribonucleic acid fragmentation and apoptotic bodies in HT-29 cells. Moreover, apoptosis was further confirmed in Canavalia ensiformis and Canavalia gladiata by increased proportion of cells in sub-G0/G1 phase. Apoptosis was induced by down regulation via tumor suppressor protein, serine/ threonine kinase and extracellular signal regulated kinase 1/2 pathways as demonstrated by quantitative reverse transcription polymerase chain reaction. The above results indicated that both lectins selectively induce apoptosis in HT-29 cellss.