From north to south they are found from Panama to northern Argentina. From east to west their range extends from the mouth of the Amazon to its headwaters in Peru and Ecuador. Both males and females of Aotus trivirgatus are similar in size with a body length of 24 to 47 cm. Tail length ranges from 22 to 42 cm.
Coats range from grizzled brown, gray or reddish backs and off white to orange undersides.
Coat color changes from one geographical location to another and for this reason, among others, A. trivirgatus is often separated into many different species or sub-species by different researchers. They have the largest olfactory bulbs and accessory olfactory bulbs of all the New World monkeys presumably due to their reliance on smell during nocturnal activity. The distinctive markings of the face include a triangular black patch between the eyes and black stripes on the sides, framing their otherwise white face. They will also complement their diet with lizards, frogs and eggs for protein. During times when food is scarce, they seek out mostly nectar, figs and insects.