A mink's fur is soft and glossy, with the American mink having fuller and thicker fur than its European cousin.

In the wild, mink vary in color from chocolate brown to almost black above, with pale fur underneath. As a general rule, the fur of northern subspecies tends to be darker than that of southern forms. Buff to white patches are common on the midline from the chin to the vent, but these vary in size and shape from one population to the next.

Domesticated mink are selectively bred especially for their fur, resulting in a range of colors from almost black to white, including many shades not found in the wild. For more information about the many colors available for domesticated mink, see True Colors!

A mink's coat helps keep it dry and also provides insulation against low temperatures. This is achieved by means of two components: guard hairs and underfur hairs.

The guard hairs are long, lustrous outer hairs whose main function is to keep the mink dry. (Marsh animals such as beaver and nutria have especially long and shiny guard hairs.) The guard hairs in a mink are thicker and longer along the center of the back, accounting for a "stripe" effect.

Each guard hair is surrounded by between nine and 24 underfur hairs which range in length from one-third to half the length of the guard hair. The function of the underfur is to retain heat, and the colder the climate a mink inhabits, the denser and woolier its underfur will be. Often the underfur is a different color from the guard hair, usually lighter.

Mink molt twice a year. The thick, dark winter coat is shed in April, to be replaced by a much flatter and browner summer coat. Come August or September, the mink molts again, and by late November its winter coat is in its prime.