This study was conducted to compare the growth‐promoting and flesh quality ‐improving effects of three active compounds in Eucommia ulmoides (EU) on grass carp (Ctenopharyngodon idella). Four iso‐nitrogenous diets supplemented with 400 mg/kg inclusion of geniposidic acid (GA), chlorogenic acid (CGA), geniposide (GP) and their combination (GA:CGA:GP = 1:1:1, the mixture) were prepared and fed to grass carp (47.1 ± 0.6 g) for 75 days. The results indicated that weight gain was increased by 5.22%, and feed conversion ratio decreased by 0.07 by dietary CGA (p < 0.05). In flesh quality, the four supplementations significantly increased muscle fibre density, total collagen and alkaline‐insoluble collagen in skin, and reduced steaming loss of flesh. In addition, dietary CGA, GP and the active compounds mixture further increased total collagen, alkaline‐insoluble collagen and amino acid in flesh. In collagen genes expression, the expression of COL1A1 in muscle and skin was significantly promoted by the supplementation of GA, CGA, GP and their combination (p < 0.05). In conclusion, the supplementation of GA, CGA, GP and their combination improved the flesh quality of grass carp, and the growth was increased by CGA. CGA played more important roles in growth‐promoting and flesh quality‐improving effects than GP and GA.