Abstract Even though Litopenaeus vannamei is one of the most important species used in aquaculture, little is known about the functions provided by the intestinal microbiota for host development. This study aims to determine the taxonomic and functional changes in the L. vannamei gut microbiota during postlarval development in a recirculation system under controlled conditions for 80 days. The results revealed that the Vibrionaceae family predominated at the beginning of the experiment, when the postlarvae weighed 0.5 to 1.5 g. The representativeness of the family Rhodobacteraceae increased to the detriment of Vibrionaceae, which showed a constant decrease as the shrimp reached the juvenile and adult stages. Finally, the Intrasporangiaceae family remained constant in postlarvae weighing 4 to 10 g. Differences in the taxonomic profile at the family level between culture days were observed through principal component analysis (PCA), where two main clusters were observed: a group of microbiota sampled at 0 D and 20 D and another of samples collected at 40 D, 60 D and 80 D, suggesting that the microbiota tend to be variable during the first postlarval phase but become more constant towards the adult phase. Microbial-mediated functions predicted by PICRUSt showed an overall functional redundancy, suggesting that gut conditions maintain the same microbiota functions regardless of changes in the taxonomic structure. These results also suggest that shrimp are under certain selective pressure favoring microbiota with specific functions according to their requirements.