A polybag experiment was conducted in glass house of Deptt of Agric. Microbiology, College of Agriculture, Raipur, Chhattisgarh during the year 2013-14 with eight treatments replicated thrice to assess the impact of Rhizobium inoculation on performance of Leucaena leucocephala (Subabul) and influence of Nitrogen on biological nitrogen fixation. The treatments comprised of inoculation with L. leucocephala - Rhizobium alone and along with 3 levels of N fertilization (N1, N2 and N3 as 50 mg, 150 mg and 400 mg N/seedling) and application of 3 levels of N alone including one control. The L. leucocephala -Rhizobium isolate is highly sensitive to antibiotic Streptomycin forming an inhibition zone of 21 mm while it is somehow resistance to Chloramphenicol (zone of inhibition was 10mm). The isolate was found good in its growth at pH range of 6.5-7.5 but can tolerate 5.0 pH. Inoculation of L. leucocephala significantly effective in increasing growth performances, further application of lower doses of N (N1 and N2) along with inoculation showed significant effect over only inoculation. Significantly maximum shoot biomass (14.35 g/seedling) and total biomass 23.81 g/seedling were obtained in Leucaena leucocephala plants receiving inoculation with N2 at 90 DAT. Nodulation was found significantly maximum (dry weight 0.32 g/seedling) in Rhizobium + N2 against only Rhizobium (0.18 g/seedling) while at control it was (0.09g/seedling). N uptake by Leucaena leucocephala significantly increased from 129.85 at control to 321.8 mg/seedling at R+N2. Seedling root inoculation with species- Rhizobium along with N2 level of nitrogen application was found most effective in increasing symbiotic traits, growth performances and N uptake by Leucaena leucocephala plants.