The Oscar (Astronotus ocellatus) is an important Amazonian species with high production potential in fish farms and commercial value for aquarists. However, limited information on the feeding characteristics, such as the frequency of daily feeding, is available for this species in captivity. Therefore, the objective of this study was to evaluate the effects of feeding frequency on growth, hematology, blood biochemical parameters, liver histology, and intestinal microbiota parameters of juvenile Oscars. Four treatments were tested, consisting of fish fed at a feeding rate of one (T1), two (T2), three (T3), or four (T4) times daily with 1% of their biomass. There were no significant differences (p > 0.05) between treatments for growth and hematological parameters. T1 showed lower serum albumin values than T2 and T4 (p < 0.05) and higher hepatosomatic index values than T4 (p < 0.05), which was corroborated by the hepatocyte nucleus count. Intestinal microbiota analysis revealed higher taxon richness in T4 than in T1 (p < 0.05). Lower feeding frequencies (T1) positively influenced the deposition of hepatic energy reserves and decreased albumin production, possibly because of lower peptide absorption in the same treatment. Based on these results, feeding frequencies of two (T2), three (T3) and four (T4) times daily were the most suitable for juveniles of this species.