Field experiment was conducted during kharif of 2012-2013 at Main Agricultural Research Station, Raichur, University of Agricultural Sciences, Raichur, Karnataka, India, to study the influence of dates of transplanting on the occurrence of insect pests on onion. The infestation of thrips varied significantly across different dates of transplanting. Transplanting of onion early in kharif season i.e., July 15th or prior dates were found to be inferior which recorded higher population of thrips (16.67 thrips/plant) and defoliators (0.46/plant) after 30 days of transplanting and similar trend was observed at 45, 60, 75 and 90 days after transplanting. Transplanting of onion during September 30th and October 15th was found to be the optimum as they harboured less thrips and defoliators. Lower incidence of thrips in September and October transplanted situation might be attributed to high relative humidity prevailed during October and November months. Onion crop transplanted during September 15th and October 15th recorded significantly higher yield (15.66 and 16.77 t/ha). Hence these dates were found to be optimum for reducing the incidence of insect pests and to achieve higher yield.