A field experiment was initiated during 2010 -11 in silty loam soil to study the effect of different cropping system and weed control practices on productivity of rice based cropping system at Pantnagar, tarai region of Uttarakhand. The experiment was laid out in split plot design with three replications. The main plots were comprised of three cropping systems i.e. rice-wheat, rice-lentil and rice-mustard and sub plots with four weed management practices viz., weedy check (W1), use of conoweeder (W2), one hand weeding at 25-30 DAT (W3) and two hand weeding at 25 & 45-50 DAT (W4) for rice and weedy check (W1), one hand weeding at 25-30 DAT (W2), two hand weeding at 25 & 45-50 DAT (W3) and stale seed bed + one hand weeding at 30 – 35 DAS (W4) for rabi crops . In 2010 and 2011, maximum yield and yield attributing characters of rice were recorded where conoweeder was used followed by two hand weeding. The major weed flora of kharif season were Eichnochloa and Cyperus and their densities observed lower with all weed management practices than weedy check. Yield and yield attributes of rabi crops were recorded higher with two hand weeding (W3) than weedy check. Major weeds observed during rabi season were Chenopodium, medicago and Melilotus and Phalaris minor. Minimum densities of weeds were found in two hand weeding (W3) during both the years 2010-11 and 2011-12. The present study shows that different cropping systems and weed management practices have significant effect on yield of crops in rice based cropping system.