Field investigation were carried out during winter season of 2011-12 and 2012-13 at Kalimpong (1250 m asl), to evaluate the effect of different fertilizer levels and weed management practices on density and dry matter of weeds and crop-weed completion for nutrient in Indian mustard (Brassica juncea (L.) Czern and Coss.). Amongst various fertility levels minimum weed density and dry matter production was recorded with the application of 150% RDF, which was found to be significantly superior to all other main plot treatments. Amongst various chemical treatments, the minimum weed density and weed dry matter production was observed with  pendimethalin (0.75 kg/ha) + hand weeding (HW) at 35 DAS, and was at par with the hand weeding twice during both the years, and in second year this was statistically similar with pendimethalin (1.25 kg/ha) and alachlor (1.25 kg/ha).  More seed yield was recorded with 150% RDF (2.19 t/ha) in first year and in second year more yield was associated with the 125% RDF (2.07 t/ha). Amongst various herbicidal treatments, during the first year maximum seed yield was registered with pendimethalin (1.25 kg/ha), and was at par with all the treatments except weedy check, fluchloralin (0.75 kg/ha) and pendimethalin (0.75 kg/ha), and in second year highest seed yield was recorded with the hand weeding twice, and was statistically at par with the pendimethalin (1.25 kg/ha), pendimethalin  (0.75 kg/ha) + HW at 35 DAS and alachlor (1.25 kg/ha). Amongst various main plot treatments, least nutrient uptake by weed was recorded with the application of 150% RDF. Least nutrient depletion by weed was registered with the hand weeding twice during both the year of data recording, and was at par with the pendimethalin (0.75 kg/ha) + HW at 35 DAS. Economics revealed that application of 150% RDF gave maximum net return   (` 19,380). However highest benefit: cost ratio (2.03) was registered with the application of 125% RDF. With sub-plot treatment highest net return (` 19,950) was observed with the hand weeding twice (` 19,950/ha), and was followed by application of pendimethalin (0.75 kg/ha) + HW at 35 DAS (` 19,850/ha). Maximum benefit: cost ratio (2.06) was recorded with the application of pendimethalin (1.25 kg/ha) and was closely followed by pendimethalin  (0.75 kg/ha) + HW at 35 DAS (1.91).