The Pomacentridae, commonly known as damselfishes, is one of the most specious families of coral reef fishes (>350 species). The genus Dascyllus contains ten species which are fall into three complexes: the aruanus, reticulatus and trimaculatus. The members of the two first complexes are small-bodied with a maximum standard length (SL) of 50-65 mm and the third complex groups large-bodied fishes of 90-110 mm SL. Phylogenetic data place the aruanus complex in a basal position with the two other species groups as derived sister taxa. Herein, we test the hypothesis that evolutionary change throughout the large-bodied species occurs by isometry. Geometric morphometrics is used to examine the ontogeny of size and shape. This method, which allows description and statistical analysis of form, is applied for the neurocranium and mandible in the three species referencing each complex: Dascyllus aruanus, D. reticulatus and D. trimaculatus. Another closely related pomacentrid, Chromis viridis, was used as outgroup for comparing ontogeny. At the larval stage, the structures are rather similar. Multivariate regression of shapes on size reveals that the three Dascyllus species have a common ontogenetic trajectory which clearly differs from that of C. viridis. During growth, allometry concerns each unit (e.g. shortening of the neurocranium and the mandible) and is identical in each Dascyllus species. However, it appears that the largest studied specimens of D. trimaculatus (90 mm SL) have similar shapes and, differ only in size from the largest ones of both other species (50-60 mm SL).