The tropical gar (Atractosteus tropicus) is one of the most important commercial species in south‐eastern Mexico, being studied in reproductive, physiological, nutrition and cultivation aspects; however, the aspects related to the endocrine system are unknown, mainly the expression of hormones during their larval development. In this study, we investigated the expression of the insulin gene (INS) and growth hormone (GH), during the embryonic period (egg), eleutheroembryon (3 DAH) up to 25 DAH using RTq‐PCR, normalized with the elongation factor gene EF1‐α. The INS phylogenetic inference showed an amino acid identity of 97%, while GH 99% against the sequence of Lepisosteus oculatus, indicating that these species are related and come from a common ancestor. The gene expression of the INS showed four peaks at 3, 7, 11 and 19 DAH, corresponding to changes in diet (Artemia nauplii) and artificial foods. GH expression was detected from the egg, increasing from day 15 to 25 DDE, concluding that A. tropicus larvae showed early and high expressions of these hormones, indicating a direct relationship with changes in metabolism of the species, increasing its function according to the nutrients present in the food and the increase in growth during the ontogeny of A. tropicus.