The experiment was conducted during kharif 2007 and 2008 to evaluate the bio-efficacy of diclosulam at different doses in soybean crop at G.B. Pant University of Agriculture & Technology, Pantnagar. Eight treatments comprising diclosulam (84 WDG) at 18, 22 and 26 g/ha, pendimethalin (30 EC) and fluchloralin (45 EC) 1000 g/ha, two hand weeding (30 and 45 DAS), weed free and weedy treatments were used in the experimental plots. Diclosulam at higher doses (22 and 26 g/ha) were found effective against grassy and broad leaf weeds at different evaluation timings as it recorded lower weed population followed by weed free, hand weeding and application of diclosulam 18 g/ha and rest of the herbicides. Diclosulam applied at 22 and 26 g/ha showed higher weed control efficiency as compared to other herbicidal treatments at all the stages of crop growth, due to broad spectrum weed control and hence higher value for all the characters of yield attributes and grain yield. Weedy plots recorded 57% lower grain yield as compared to weed-free treatments. Application of diclosulam at 22 and 26 g/ha produced maximum grain yield which was similar to yield found in weed free treatment during both the years