Onion is an important vegetable spice crop of India having high domestic demands and export potential. Weeds can cause considerable losses to onion yield and monocot weeds viz.; grasses and sedges cause higher competition due to similar biology and ecological niches. Critical period of crop weed competition for onion depends upon seasons, soil and climatic conditions and is generally regarded as 15-45 days after transplanting. Manual weeding is highly cost intensive while mechanical hoeing is difficult owing to narrow spacing. Therefore, selective pre- and post-emergence herbicides assume key role in monocot weed management. Integrated weed management modules including cultural and mechanical methods with judicious herbicide application should be promoted for improving weed control efficiency, environmental health and sustainability.