||Due to various pharmacological properties, including antioxidative, anti‑inflammatory and antibiotic properties, royal jelly (RJ) has been widely consumed in daily diets in numerous countries. In the present study, the effect of RJ on 4T1‑bearing mice was investigated. The study was performed by feeding 4T1‑bearing mice with RJ using either the prophylactic‑therapeutic (PTRJ) or therapeutic (TRJ) method. The experimental results for the PTRJ group demonstrated that the weight of tumor was significantly reduced (RJ 0.5 and 1.5 g/kg); and in the serum, the levels of interleukin (IL)‑2 (RJ 0.5 and 1.5 g/kg), interferon (IFN)‑α, superoxide dismutase (SOD) and total antioxidant capacity (T‑AOC) were significantly elevated, but the concentrations of IL‑4 (RJ 0.5 and 1.5 g/kg) and IL‑10 (RJ 1.0 g/kg) were significantly decreased. In addition, the activities of T‑AOC and glutathione reductase (GR) were significantly improved in the liver, whereas in the kidney, the activities of T‑AOC and GR were significantly increased only under the dose of 0.5 g/kg. For the TRJ group, the antitumor effect of RJ was not significant; the change in IL‑2, IFN‑α, SOD and T‑AOC levels in the serum, and the change in T‑AOC and GR in liver were similar to those observed in the PTRJ groups. RJ treatment was demonstrated to reduce the development of breast tumor in mice, and simultaneously improve the antioxidant capacity of the serum, liver and kidney, particularly using the prophylactic‑therapeutic method. These results corroborated the efficacy of RJ supplementation in diets. The results of the present study suggest that the antioxidant and immunomodulatory activities of RJ serve an important role on antitumor growth.