The relationship between the solitary koinobiont endoparasitoid Misotermes mindeni Disney and Neoh (Diptera: Phoridae) and its termite host Macrotermes gilvus (Hagen) (Termitidae: Macrotermitinae) was examined. Misotermes mindeni were reared from parasitized M. gilvus major soldiers in the laboratory. Adult female parasitoids were on average larger (4.67 ± 1.29 mg) than males (3.73 ± 1.18 mg). The influence of the size of the parasitoid on its fitness was studied under laboratory conditions. No relationship was found between adult female size and the number of laid eggs, but weak positive relationship was observed between adult male size and longevity. The sex of emerging adults of M. mindeni was correlated positively with the size of the major soldiers of M. gilvus. Females emerged from the larger hosts, whereas males emerged from the smaller hosts. The host size ranges differed between the sexes. This may suggest that the parasitoids modified the size of their hosts. The body sizes of both female and male parasitoids at pupal and adult stages were significantly correlated with host size, such that larger hosts ultimately yielded larger parasitoids and smaller hosts yielded smaller ones.