Bambara groundnut (Vigna subterranea (L.) Verdc.) is a legume cultivatd majorly for it’s seeds and commonly grown by subsistence farmers in sub-Saharan Africa. In order to determine the effect of ethyl methane sulphonate (EMS) mutagen on the growth, yield and some physiological parameters of non-water stressed (NWS) and water stressed (WS) bambara groundnut. It’s seeds were treated with five concentrations (0.00 (control), 0.25, 0.50, 0.75 and 1.00% v/v) Ethyl methane sulphonate and were grown under two conditions: non-water stressed and water stressed. Analysis of variance (ANOVA) revealed significant differences (P ≤ 0.50) in the emergence percentage (6 DAS), germination percentage (7 DAS), plant height (PH), number of leaves per plant (NL), leaf length (LL), leaf width, (LW), relative water content (RWC), chlorophyll a, b and total chlorophyll contents in the non-water stressed and water stressed plants. After rewatering at 8 WAS, highest number of leaves in NWS and WS conditions were observed in 0.75% EMS concentration (229, 189), highest leaf length in NWS and WS plants were observed in 0.50% EMS concentration (9.47cm, 9.13cm). Highest leaf width in NWS and WS plants was observed in 0.25% EMS concentration (4cm, 3.63cm). Highest number of pods per plant (NP) and weight of pods per plant (WP) were observed in 0.75% EMS concentration only in NWS plants. Highest chlorophyll a, b and total chlorophyll content was observed in 1.00% EMS concentration. The result form this study showed that Ethyl methane sulphonate (EMS) mutagen concentration increased the growth, yield and physiological parameters of Bambara groundnut in non-water stressed condition at different doses, however there was no positive effect of EMS on yield in the water stressed plants.