Rapeseed/Mustard crop is being widely promoted as a matter of crop diversification and significant emphasis is being laid on saving the crop from insect pests as scientists are continuously striving their best for the betterment of the quality of the produce of the crop. This research was conducted to determine the efficacy of different insecticides against the mustard aphid which causes significant yield losses in Brassica juncea. Study was conducted during crop season 2016-17 using RCBD design with 3 replications, data were recorded at different recommended time intervals. Maximum mortality of mustard aphid was caused by Advantage (98.70%) followed by Plenum (96.60%), Oshin (87.10%), and Pirate (49.60%). Advantage and Plenum represented least differentiated mortality percentages while results of Pirate treatment showed a possible indication of resistance development in insects against this particular insecticide.