The long fur of red fox gives them an appearance of being larger than they really are.

Red fox commonly weigh 10 to 12 pounds in many areas with occasional large specimens weighing up to 14 pounds. Red fox are slightly heavier in the northern parts of their ranges, and slightly lighter in far southern locations.

Distinctive marks of red fox include feet that are usually black, with black fur also on the backs of the ears. A white tipped tail is common, and the red colors of the fur mute with grayish or whitish fur on the throat, bottom of the neck and belly areas. Colors vary in sections and with individuals. Many southern red fox are blondish, and darker reddish colors are usually found in northern farmlands and forests. Red fox on the western high plains are somewhat pale in color.

Color phases do occur with red fox, even in the same litters. Color phases are much more apt to occur in northern or colder regions and almost never occur in southern regions. Other than the most common color of red, red fox can be black, silver or a cross between red and silver, known as "cross fox". Black fox have black tipped guard hairs, and silver fox are black with white tipped guard hairs.

Cross fox often have reddish sides and dark along the middle of the back area, with a cross of dark colored fur running from one front leg over the back to the other front leg. Relatively uncommon are red fox known as "bastard" fox and "Sampson" fox. Bastard fox lack color and are brownish or greyish in color. Sampson fox have few or no guard hairs in their fur.

The eyes of the red fox are yellow or amber in color, with elliptical pupils. Red fox also have 42 teeth, including 4 canine teeth to help them catch and kill prey species.