Abstract: Effect of different concentrations of three pre-emergence herbicides namely, pendimethalin (N-(1-ethylopropyl) 2,6-dinitro-3-4-xylidine), trifluralin (2,6-dinitro-N-N-dipropyl-4-trifluoromethylaniline) and oxadiazon (3-(2-4 dichloro-isopropoxy Phenyl) -5-t-butyl -3, 4 oxadizaolin 2-one) on nodulation, nitrogen fixation, morphological characters and some other parameters have been investigated in groundnut (Arachis hypogaea), L. cv Banki. Pendimethalin at 0.74, 1.49, 2:23, trifluralin at 0.37, 0.75, 1.20 and oxadizon at 0.30, 0.60, and 0.90 kg ha–1 was incorporated in soil before sowing. Data were recorded 40, 70 and 90 days after germination. Recommended doses of these herbicides in general had no significant effect on different parameters under investigation. Higher doses of these herbicides adversely affected the nodulation and the fresh and dry weights of nodules. However higher concentration of oxadiazon resulted in increased N accumulation in shoots of groundnut plants. It was concluded that the herbicides under investigation did not affect the groundnut plants adversely if used at recommended levels.