Diachasmimorpha longicaudata (Ashmead) is an endoparasitoid of fruit flies reared for augmentative biological control of several species of Anastrepha in Mexico. During the production of D. longicaudata different sizes of parasitoids are produced depending on the host size. Here, we investigated whether host size influences the biological and behavioral parameters of the wasp that emerged under laboratory conditions. Three different sizes of host (small, medium, and large) were used for the experiments. Host size significantly affected the number of parasitoids emerged as greater number of parasitoids emerged from medium size hosts compared to small and large hosts. The ratio of females to males did not differ among the groups. Host body size influenced life expectancy of parasitoid females and males deprived of food, and parasitoids that emerged from large hosts lived longer. In contrast, host body size did not significantly influence the life expectancy of parasitoid females and males provided with food ad libitum. Host body size also affected gross and net fecundity of emerged parasitoids; females that emerged from medium and large host larvae were more fecund. Host size did not affect most of the behavioral parameters evaluated, except the time of landing on source. Females that emerged from large host larvae spent less time before landing on a host source than females from the smaller hosts. Host body size did not affect the different trajectory indices evaluated, except the mean walking speed of D. longicaudata. Females developed in large hosts showed an increase walking speed compared to females from medium and small hosts.