It turns out that all species of deer, including white-tailed deer, do exhibit some nocturnal tendencies. However, deer have several adaptations to help them avoid predators when they’re at their most vulnerable during the day, such as unique coats or camouflage.
So depending on how you look at it, deer could have characteristics of both diurnal animals (active during daytime) and nocturnal animals (active at night). Technically, though, deer are neither nocturnal nor diurnal but rather a crepuscular creature, meaning they are mainly active during the twilight hours.