This study, based on three years of mating behavior observations and 10 years of birth records, reveals that Sichuan golden monkeys in captivity displayed a marked seasonality of mating behavior and births. The peak of matings occurred around October, and births occurred in March-June. The birth peak followed the mating peak by six to seven months. This seasonal cycle of matings and births was similar to observations made in the wild, where both temperature and food resources were favorable in spring. The time delay between peaks of matings and births was the approximate length of gestation, which implies that mating behavior was concentrated during the period of conception. We suggest that the peak of births in captive Sichuan golden monkeys occurred during the time of year with the most favorable environmental conditions, and the peak of matings corresponded with the period of conception.