White-tailed deer (Odocoileus virginianus) are one of the most abundant and well-studied ungulates in North America. Few studies, however, have examined how population demography affects the fawning season, which may be influenced by age structure and adult sex ratio of the population. From 2010 to 2013, we used vaginal implant transmitters (VITs) to record the birth date of fawns born within a 174-ha captive facility to elucidate how population demography affects fawning season. We documented an earlier shift in fawning season as male age structure increased from a mean of 2.74 years old in 2010 to 3.92 years old in 2013. Prior to the shift, the mean fawning date was 12 August, and after an increase in population age structure, the mean fawning date was 30 July. An earlier fawning season may be important for neonatal survival, especially in areas of the Southeast where coyotes (Canis latrans) may limit recruitment. The effect of male age structure on the timing and duration of the fawning season has yet to be firmly established, but we predict managers can increase neonate development and survival by increasing male age structure.