A study was carried out to evaluate the effect of early post emergence herbicide, imazethapyr against weeds in irrigated soybean (Glycine max (L.) Merill) at Agricultural Research Station, Bhavanisagar. Weeds, viz., Dactyloctenium aegypticum, Acrach ne racemosa, Cyperus rotundus, Boerhaavia diffusa, Digera arvensis, Parthenium hysterophorous were the dominant weeds in the experimental field. Imazethapyr at 100 and 200 g ha -1 applied on 15 DAS provided 87 to 91% weed control efficiency compared to unweeded control. However, imazethapyr at 200 g ha -1 had slight phytotoxicity on soybean in the initial stages. Higher grain yield of 1645 kg ha -1 was obtained with application of imazethapyr 100 g ha -1.