Mule deer and whitetail deer differ in several notable ways. Mule deer are generally larger, weighing about one hundred pounds more than whitetail deer, and they are typically found farther west in North America. The antlers of mule deer are also larger, taller, and have a wider spread compared to those of whitetail deer.

A key distinguishing feature between the two species lies in the branching pattern of their antlers. Mule deer have antlers that fork, with each branch then forking again, creating a distinctive pattern. In contrast, whitetail deer antlers consist of a single main beam from which each tine branches off individually. This difference in antler structure makes it relatively easy to tell the males of the two species apart in the field.

As one would expect, these species also differ in the look of their tail. Whitetails have a tail that is brown on the dorsal surface and white on the underside. When raised, it looks like a big fluffy flag and serves as a warning. Mule deer, on the other hand, have a skinnier tail with a black tip. They rarely raise their tail when fleeing; instead, their intraspecific warning system is their telltale gait, the stot. When animals stop, they lift all four legs off the ground at the same time. It is a very efficient movement for moving over sagebrush.

The final difference, and perhaps the most amusing, lies in the overall appearance of their faces. Mule deer possess prominent brow ridges that give them a somewhat rugged or "ugly" look, especially when contrasted with the gentle, softer facial features of the whitetail deer.