[5] Common brown lemurs are unique amongst Eulemur in that they exhibit little-to-no sexual dichromatism: in both males and females, the face, muzzle and crown are dark gray or black, with white or tan "cheeks" of varying thickness.

The short, dense fur of the body is primarily brown or gray-brown, with a lighter gray or tan underside.

The fur on the back of their hands is often a medium orange or reddish color, and their long, bushy tail may either be similar in color to the dorsal pelage or, more commonly, a darker shade of gray, black, or brown.

There is also some overlap with the black lemur in northeast Madagascar in the Galoko, Manongarivo and Tsaratanana Massifs.

[9] These lemurs show linear hierarchy, adult female dominance, and the presence of conciliatory behavior after aggressions.

[5][6] Sexual maturity occurs at about 18 months,[5] and females give birth to their first young at 2 years old.

[6] The common brown lemur's diet consists primarily of fruits, young leaves, and flowers.

[4]: 272–274 [6] The common brown lemur from a Brazilian zoo was found to be a host of an intestinal acanthocephalan parasitic worm,Pachysentis dollfusi.