Natural parasitism of Doryctobracon areolatus (Szépligeti) (Hymenoptera: Braconidae) on various development stages of Anastrepha obliqua (Macquart) (Diptera: Tephritidae) attacking Spondias mombin L. fruits was studied under field conditions. We collected 120 fruits of S. mombin from which we got 495 A. obliqua larvae of different instars. A total of 88% of these larvae were parasitized. Within the parasitized cohort, the first-instar of D. areolatus was frequently detected in all 3 larval stages (L1 = 94.3%, L2 = 98.1%, and L3 = 100%), and the rest (i.e., L1 = 5.7%, L2 = 1.8%) corresponded to the presence of eggs. In fruits with controlled infestation and cage-induced parasitism under field conditions, D. areolatus oviposited in mature eggs and recently hatched larvae of A. obliqua with comparable frequencies. Seven preimaginal stages of D. areolatus were observed during their development, which was completed in 27 days. It is concluded that D. areolatus has the capacity to oviposit in embryo eggs and neonate larvae of A. obliqua and that its first-instar larvae (with three distinct sizes) are capable of synchronizing their development with the development of the host larvae. This finding represents the first report of a native parasitoid attacking eggs or neonate larvae of a tephritid in the Neotropics. The implications of this finding are discussed within the context of the competitive interactions of this species with other parasitoid species under sympatric conditions, as well as the relevance for developing laboratory rearing methods for biological control purposes.