Efficacy of azimsulfuron was studied for controlling broad spectrum of weeds in transplanted summer rice. All the herbicidal treatments were significantly superior to weedy check. There was more than 48% reduction in the grain yield of rice due to competition with weeds in the weedy plots. Azimsulfuron at 30 g a.i. ha^-1 was found effective in reducing the population of predominant sedges viz., Cyperus difformis and Fimbristylis miliacea and broad leaf weeds viz. Sphenochlea zeylanica and Marsilea quadrifolia. However, complete suppression of all the major weeds including late emergent grassy weed, Leptochloa chinensis, was recorded at the application rate of 35 g a.i. ha^-1. The highest grain yield (6.02 tonnes ha^-1) and N-use efficiency (60.0) were obtained in weed free check. Among the tested doses, azimsulfuron at 35 g a.i. ha^-1 applied 18 days after transplanting was found to be the most effective (weed control efficiency 98.5%) in controlling the complex weed flora and produced comparable grain yield (5.95 tonnes ha^-1) with weed-free check, thereby realizing an increase of 91% yield over weedy check. The N-use efficiency (59.5) was also higher in azimsulfuron (at 35 g a.i. ha^-1) treated plots.