Acetamiprid (AP) is a fairly new neonicotinoid insecticide. Its indiscriminate use both in agriculture and domestic areas against wide range of pests such as aphids and whiteflies is causing toxicity to man and animals. In recent years the effects of insecticides on immune response have received more attention. The present study was designed to evaluate the toxic effect of repeated oral (by gavage) administration of AP over six weeks on humoral immune response. Forty eight adult male Sprague Dawley rats were divided into four groups (12 animals each). Animals of the 1st group were untreated and served as control , rats of the 2nd group were orally given 1/ 10 LD50 (83.18 mg/ kg b. wt.) , animals of the 3rd group were administered orally vitamin C alone at a dose level of 200mg / kg b.wt, every other day for six weeks , rats of the 4th group were given AP similar to those of the 2nd group then administered orally with vitamin C similar to those of the 3rd group 30 minutes after each AP administration. At day one after the end of experiment , eight rats were picked up randomly from each group , blood samples were collected from each animal under slight ether anaethesia through heart puncture into plain vaccutainer tubes and sera were separated. Data obtained revealed that oral AP administration into rats induced a non significant increase in IgM level ; significant decrease and  increase in IgG and IL – 6 levels respectively as compared to the control values. Supplementation with vitamin C potentiated significantly the effect of AP on IgM , WBCs count , monocytes and lymphocytes percentage , and reduced significantly its effects on IgG and IL-6. These data indicate that AP is capable of inducing changes in humoral immunity that could be selectively modulated by supplementation with vitamin C.