Biological control using an ectoparasitic idiobiont (e.g., Pachycrepoideus vindemmiae Rondani) (Hymenoptera: Pteromalidae) can be an effective approach to reduce the economic losses caused by the melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae). In this study, we determined the parasitism of P. vindemmiae on B. cucurbitae pupae of different ages. The results showed that B. cucurbitae pupae at all ages could be successfully parasitized by P. vindemmiae. The higher numbers of pupae parasitized (10.12 to 9.32 pupae/day for no-choice tests and 8.0 to 7.82 pupae/day for choice tests) were achieved when 3 or 4-day old pupae were used as hosts. The selection coefficient revealed that P. vindemmiae preferred 3 or 4-day old pupae as the host. Pachycrepoideus vindemmiae females developed more quickly on 3 or 4-day old hosts than on pupae of other ages. Longevity of parasitoid offspring obtained from 2 and 7-day old melon fly pupae varied from 9.45 to 10.37 days and from 8.97 to 9.45 days for females and males, respectively. The emergence rate and proportion of female offspring of P. vindemmiae were not affected by the age of the pupae. However, our results indicate that the performance and suitability of P. vindemmiae were affected by the age of the host pupa age. Our findings may be useful for the development of biological control programs for B. cucurbitae.