Ongoing discussion on the taxonomic status of Anastrepha fraterculus (Wiedemann) and limited biological knowledge of this species emphasize a need for information on sexual behavior and mating compatibility among populations from different ecological regions. In this study, we studied four populations of A. fraterculus from different fruit-growing and biogeographical areas in Argentina, i.e., Yuto and Horco Molle from the northwest and Posadas and Concordia from the northeast. Pair-wise compatibility tests were performed for all possible combinations. Virgin males and females, in the proportion 1:1, were released into field cages containing a tangerine tree (Citrus reticulata Blanco). Sexual behavior was recorded in each cage. To determine the degree of mating compatibility between any two populations, sexual isolation indices and male and female performance indices were calculated. The values of the sexual isolation index did not differ statistically from the expected value (zero) under the assumption of random mating. This result indicates that A. fraterculus populations are fully mating compatible in Argentina, thus encouraging the application of the sterile insect technique to control this species in the region. Differences found between some populations in copulation duration and couple location in the cage suggest that variability might exist for these traits, requiring confirmation in the future.