Pesticide use is effective for the protection of plants from pest, but the extensive use of pesticide over the past four decades has resulted in the disturbance of natural biological system. Some pesticides used in agriculture can be harmful to nitrogen fixing bacteria. The objective of the present study was to study the effect of pesticides on nitrogen fixing bacteria. The study was actually carried out for observing the effect of pesticides Hilcyperil and Nuvan on desired nitrogen fixing bacteria, Rhizobium spp. and Azotobacter spp. which are very essential for the growth of plant as well as for more yields. Nuvan pesticide greatly inhibited the growth of both the nitrogen fixing bacteria as compared to that of Hilcyperil. It is concluded from this study that the pesticides have differential effect on the growth of nitrogen fixing bacteria, and their action vary at different sites. Indication has been observed that the pesticides which are under field condition possibly due to its high toxic nature reduced the population of these bacteria under field condition.