Fisher are usually dark brown in color. Males oftentimes have a lighter grizzled coloration on the face, head and over the shoulders. The longer guard hairs in the fur are 1 1/2 to 2 inches on the body and 1/2 inch longer on the tail. The fur on males is much coarser than on the females and both are darkest on tail and legs. Two small, white patches of fur are found in the front armpit areas.
Males may measure 36 inches or longer and adult males often weight 10 to 12 pounds. Males rarely weigh more than 14 pounds. Females weigh about 1/3 of the average weight of males and most females are about the size of large mink, although their longer fur makes them appear to be larger. Typical females weigh between 4 and 5 pounds.
Fisher have 38 teeth, including four sharp canine teeth and flat topped molars to aid in chewing. Five toes register in fisher tracks and the inside toes are smaller and placed behind the other four. The fisher cannot retract it's claws and they are usually dulled somewhat by constant contact with the ground and rocks.
A pair of anal musk glands are present on both males and females and their musk is often released when the fisher is frightened or angry.