The effect of a chitin synthesis inhibitor (Lufenuron) on the antennal segements and their sensilla of cowpea beetle, Callosobruchus maculatus (Fabricius) was studied by using scanning electron microscope. Seven types of sensilla were recognized on both untreated and treated antennae with 9 ppm of lufenuron, including Böhm bristles (BB), two types of sensilla trichodea (ST₁, ST₂), sensilla chaetica (SC), two types of sensilla basiconica (SB₁, SB₂) and grooved peg (GP). The functions of these sensilla were discussed in relation to their position on the antenna. Significant difference in lengths of most segments of the antennae between untreated and treated beetles was observed. A significant difference in lengths and diameters of nearly all types of sensilla was recorded. The highest increase in length of sensilla was noticed for the sensilla chaetica followed by sensilla trichodea. These types are used by insects as mechanosensory, sex pheromone and gustatory receptors that help them to make a decision to select their food and oviposition sites.