Out of 6 different native Rhizobium strains viz., A1, C10, G7, Gn2, Gn3 and S8 of Assam soil Gn3 proved to be the most potential strain exhibiting significantly higher level of nitrogenase activity (479.01 mole g-1h-1) as well as vegetative and yield attributes of cowpea. At 50% level of recommended chemical nitrogen, the maximum number of root nodules (112.67) and their fresh and dry weight (2.04 and 0.71 g) were observed in the roots of Gn3 inoculated plants. However, at recommended dose of chemical nitrogen the maximum green pod production (38.03 q ha-1) could be obtained from Gn3 inoculated crop which was 31.14% increased over the uninoculated control with recommended fertilizer and at par with the production (37.83 q ha-1) obtained by the inoculation of the same strain at 50% dose of recommended fertilizer nitrogen which is only 0.69% lower than the percentage increase in production at recommended dose of fertilizer nitrogen.