Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) is an effective idiobiont ectoparasitoid of the psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae), vector of the huanglongbing (citrus greening disease) pathogen. We examined the external and functional morphology of the antennal sensilla of adult male and female T. radiata by using scanning and transmission electron microscopy, respectively, to gain insights into the behavioral ecology of this parasitoid. The geniculate antennae of male and female T. radiata were composed of a long scapula-shaped scape with a basal radicula, a barrel-shaped pedicel, and a long flagellum with a basal ring-like annulus. Five morphologically distinct sensilla, including two types of aporous trichoid sensilla (AST-1 and AST-2), one multiporous trichoid sensillum (MST), one multiporous placoid sensillum (MPS), and one aporous basiconic capitate peg sensillum were identified on the antennae of both sexes. The antennal structures of T. radiata were sexually dimorphic. Male antennae consisted of four funicular flagellomeres and possessed a greater number of olfactory MST than female antennae, suggesting their possible function in perception of mate-related volatile cues. Female antennae were characterized by three funicular flagellomeres and a greater number of MPS than male antennae, suggesting their possible function in the perception of host-related volatile cues. The results are discussed in relation to plausible roles of the identified sensilla in mate and host location by this important parasitoid species.