Tepary bean is an important food legume. The genetic improvement of the crop is limited by a narrow genetic base but this genetic base can be broadened through induced mutagenesis. This study was designed to determine the (i) effects of chemical mutagenesis using ethyl methane sulfonate (EMS) on M 1 seedlings (ii) the adult plant performance of M 2 - M 4 generations and (iii) the relationships between growth attributes at the seedling and adult plant stage. Mutagenized seed with varying doses of EMS was germinated at room temperature in order to raise M 1 seedlings. There were highly significant (P < 0.01) differences due to dose effects among the seedlings. The highest LD 50 (3.37 % EMS v/v) was observed for ‘Genotype 3’. Under field conditions, all the three factors influenced the plant performance. The results demonstrated the potential of EMS to induce genotypic variation and desirable agronomic traits in tepary bean.