Abstract: Genetic improvement of onion (Allium cepa L.) by conventional methods of hybridization is slow due to its highly heterozygous, outcrossing and biennial nature. To augment this process induced mutagenesis could serve as a useful tool. Keeping this in view, the present study was conducted to test the efficacy of Ethyl Methane Sulphonate (EMS) and Sodium Azide (SA) in inducing variability in onion. For this purpose, seeds of six onion varieties were soaked in solutions of different concentrations of EMS (0.1, 0.15, 0.2, 0.25%) and SA (0.1, 0.3, 0.5, 0.7%) for 4 h and their sensitivity towards these mutagens was assessed in terms of seed germination and seedling growth. Significant differences (p<0.01) were observed in the varieties and treatments with respect to the traits studied. Lower dose (0.1%) of both SA and EMS showed stimulatory effect on germination potential of seeds of all except variety-4 and variety-5. Shoot length was enhanced over control in variety-3 and variety-5 at 0.1% SA and variety-4 at 0.1% EMS. Root length was slightly higher than control in variety-3 and variety-4 at 0.1% SA and 0.1% EMS, respectively. Reduction in all the three traits was observed at higher doses of EMS and SA in all the varieties. The reduction in shoot and root length was more pronounced under SA treatment than EMS. Also, germination process was more sensitive to mutagens than the seedling growth. The present study demonstrated that both mutagens at low dose could be suitable for the creation of variability in onion.