Four vegetable seed oils viz.,Bitter gourd (Momordica charentia), Small bitter gourd (Momordica dioica), Bottle gourd (Lagenaria siseraria), Ridge gourd (Luffa acutangula) seed, solvent extracted oils were evaluated against mustard aphid, Lipaphis erysimi Kalt., in the farm of mustard crop. All the natural insecticides (Vegetable oils) were found very effective and caused 100% mortality (indicated by non-motility of the insects) at 6% conc. in 24 hrs. Seed oil of Small bitter gourd and Bottle gourd were found to be satisfactory natural insecticide giving 100% mortality at 4% conc. in 24 hrs. Lower concentrations up to 2% was also found effective but require longer time (up to 32 hrs.) to give 100% mortality in case of Small bitter gourd and Bottle gourd. No further spray was given to crop and also no further infestation of aphid found in the vegetable oil treated crop.