To investigate the long-term effect of feeding royal jelly (RJ) on the testicular function, 32-week old male golden hamsters were fed diet containing RJ at doses of 0 μg/g diet (control), 50 μg/g diet or 500 μg/g diet for 12 weeks. At the end of the experiment, the hamsters were assessed for testicular function in terms of the amounts of intra-testicular free testosterone (TS) and histopathological changes. RJ diet groups showed higher TS levels and more intensive spermatogenesis than the control group in a dose-dependent manner. The intensity of spermatogenesis and TS levels in the 500 μg of RJ/g diet group showed significant differences of p < 0.01 and p < 0.05, respectively, when compared with those in the control group. These results indicate that the long-term feeding of RJ inhibits the age-associated decline in the testicular function of male hamsters.