The effects on the apparent digestibility, antioxidant activity, milk production, component, and fatty acid (FA) profiles were evaluated in dairy goats fed a varying red yeast rice polyphenol extract (RYRE) content. Thirty-two dairy goats were randomly allocated into 4 treatments. The goats were fed a basal diet (CON) or a diet supplemented with 1, 2, or 3 g/kg of RYRE. The results indicated that apparent digestibility of neutral detergent fiber and acid detergent fiber was significantly affected by treatments, and increased linearly and quadratically with increasing RYRE supplementation (P < 0.05). The total antioxidant capacity, glutathione peroxidase, and catalase increased quadratically, and the malondialdehyde concentration decreased quadratically with increasing RYRE content (P < 0.05). The milk production parameters and n-3 polyunsaturated fatty acids (PUFAs) increased linearly and quadratically (P < 0.05) with increasing RYRE supplementation. The L* value and n6/n3 ratio decreased linearly and quadratically, and the a* value and milk lactose increased quadratically with increasing RYRE supplementation (P < 0.05). The total volatile fatty acid and propionic acid increased quadratically, whereas the acetic acid and acetate:propionate ratio decreased quadratically with increasing RYRE supplementation. Overall, diets supplemented with RYRE enhance apparent digestibility, antioxidant activity, promote milk production, increase milk n-3 PUFAs, and improve rumen fermentation of lactating dairy goats, with the 2 g/kg RYRE treatment having the optimal effects under the conditions of this experiment.