The external morphology of the dogwood borer, Synanthedon scitula (Harris) (Lepidoptera: Sesiidae), antennae and their sensilla was investigated using light and scanning electron microscopy. Male and female antennae were clavate before tapering to an apical point and consisted of three main segments; scape, pedicel, and flagellum. Although there was no significant difference in the length of the flagellum between genders, the number of flagellomeres was significantly greater in females than in males and the length and width of individual flagellomeres was significantly greater in males than in females, except near the proximal and distal end of the antennae. The antennal flagellum of both male and female dogwood borer contained seven sensillum types: auricillica, basiconica, chaetica, coeloconica, squamiformia, styloconica, and trichoidea (three subtypes). The mean number of sensilla basiconica did not differ between female and male antennae, but all other sensillum types were significantly more abundant on female antennae. The morphology and purported function of each sensillum type are discussed in relation to the host and oviposition site finding and acceptance behaviors exhibited by dogwood borer.