The effects of dietary supplementation with Citrus × latifolia essential oil (EOCL: 0, 0.25, 0.5, 1.0 and 2.0 ml EOCL/kg diet) on growth, survival, gut tract morphology and the metabolic and oxidative parameters of tambaqui (Colossoma macropomum) were investigated in a 60‐day experiment. The inclusion of up to 2.0 ml EOCL/kg diet did not promote growth; however, fish fed 1.0 and 2.0 ml EOCL/ kg diet presented higher survival and all EOCL groups had increased intestinal fold height and length compared to the control group. After 60 days of experiment, glucose, glycogen, lactate and protein levels in the liver and muscle were altered significantly by dietary addition of EOCL. The muscle LPO content was higher in fish fed 2.0 ml EOCL/ kg diet than the control group. The reactive oxygen species content was higher in the liver but lower in the muscle of fish fed 1.0 ml EOCL/kg diet compared to the control group. SOD activity was higher in the liver of fish fed 0.50 and 1.0 ml EOCL/kg diet than the control group. Therefore, dietary addition of 1.0 ml EOCL/kg diet is advisable for tambaqui juveniles since it improved survival, the antioxidant capacity of tissues and the intestinal absorption area.