Mountain anoas look like deer, but are actually water buffalo. They weigh between 150 and 300 kg. Mountain anoas have a woolly coat that is a dark brown or black in colour, but changes between February and April after they moult. After moulting, the woolly underfur of the animal is shed, and light spots appear on the head, neck and limbs. The head develops white spots on each side of the cheek, while the front side of the neck develops a crescent-shaped light spot. Light spots also develop right above the hooves. The fur on the neck becomes shorter, while long hairs remain on the body.

Mountain anoas also have horns. These horns are flat in the front, but become triangular from the mid-section to the ends.