Onion (Allium cepa L.) is one of the most important vegetables in family Alliaceae, which is cultivated worldwide. In onion, weeds are among one of the major concerns which cause its yield reduction. The present study was designed to assess the effectiveness of different methods for weed control in onion. In this study, five treatments were selected including control, black polythene mulch sheet, white polythene mulch sheet, Dual Gold spray @ 9.0 mL L-1 and Preact spray @ 7.5 mL L-1 to control weeds. The weedicides were applied as pre-emergence sprays before transplanting the seedlings. The experiment was laid out in Randomized Complete Block Design with three replications. From the results, it was concluded that there were significant differences among the studied weed control treatments. Among the five treatments, greater plant height (33.0 cm), number of leaves per plant (8), bulb diameter (4.7 cm) and bulb weight (73 g) were observed in the ridges covered with black mulch sheet. However, the minimum weed biomass (fresh and dry) was recorded in black mulch sheet and Preact pre-emergence weedicide spray (140 and 80 g in both). Thus, black polythene sheet as mulching material was found better option for weed management in onion fields.