Salinity is one of the major abiotic stresses that affect crop productivity worldwide. It adversely affects plant growth and development and results in reduction of dry matter and yield. Growth and productivity of mungbean is affected adversely by different levels of salinity. An experiment was conducted in Department of Plant Physiology, Bidhan Chandra Krishi Viswavidyalaya Mohanpur, Nadia, West Bengal to study the effect of salinity stress on seedling growth in mungbean [Vigna radiata L. Wilczek] and to attain an idea about the physiological basis of salt tolerance. Eighteen genotypes of mungbean were used in the study. The salt stress was imposed using a solution of 100mM NaCl. The results indicated that all the genotypes, in general, exhibited reduction in seedling growth under salinity stress. On the basis of relative performance of the genotypes under salinity stress for seedling characters, four most tolerant (SML 1205, IPM 99-1-6, IPM 2K-14-9 and CZMK-1) and four most susceptible genotypes (Pusa 032, Pusa 1131, IPM 99-1-10 and Pusa 1172) were identified and were subjected to further physiological studies. The susceptible genotypes registered greater decrease in chlorophyll a and b content in their leaves than the tolerant ones. An increase in leaf protein in the tolerant genotypes in response to stress exposure in the present study might be attributed mainly to the increased synthesis of stress proteins. The activity of nitrate reducatse decreased under salinity stress in all the genotypes. The higher activities of catalase helped the tolerant genotypes to combat against salt-induced oxidative stress in much better way than the susceptible genotypes.