The aim of this study was to investigate the effects of dietary Citrus x aurantium essential oil (EOCA) on the growth and intestinal histomorphology of silver catfish (Rhamdia quelen) fingerlings. Five diets with different doses of EOCA (0.0, 0.25, 0.5, 1.0, and 2.0 mL/kg diet) were evaluated. At the end of 60 days, the growth performance was positively correlated with dietary EOCA supplementation. The results showed an increase in fold height in the middle intestine (MI) of fish fed the EOCA diet compared to the control group. In the anterior intestine (AI), the enterocyte height increased, while the goblet cell number decreased in all EOCA-supplemented diets. The goblet cell number in the MI and posterior intestine (PI) was higher with EOCA and lowest in the control group. Diets with EOCA did not affect the fold height in the PI. Similarly, to the AI, the fold width in PI increased in the 0.5 mL/kg treatment compared to the control group. These results revealed that dietary supplementation with EOCA, primarily at a dose of 0.5 mL EOCA/kg diet, promoted positive effects on the intestinal morphology of R. quelen, indicating that the use of EOCA extracted from sweet orange peel, a fruit residue, could be considered in fish diets.