The Junín red squirrel is a relatively large tree squirrel, having a head-body length of about 25 cm (9.8 in). The majority of the body is covered in dark red fur, grizzled with black, fading to a chestnut brown on the tail, which is slightly shorter than the combined head and body. The underparts vary in colour between individuals, being white, red, or some shade in between. The whiskers and the edges of the ears are black.