Puku stand about 80 cm (31 in) at the shoulder and weigh from 70 to 80 kg (150 to 180 lb). The puku is sandy brown in colour, with the underbelly a slightly lighter brown. The coat is rougher than the similar-sized southern reedbuck, lechwe or impala, or the smaller oribi. Males have 50-cm-long, ridge-structured horns which are very vaguely lyre-shaped.
Puku are found almost exclusively in marshy grassland and dambos, where they eat grasses. Puku are crepuscular, active in the early morning and late afternoon. When scared, puku repeat a shrill whistle sound. Females gather in herds of up to 20 individuals. During the rainy season, many herds will come together for added safety, typically reaching around 50 females. Males hold territories and attempt to persuade herds of females to stay within their territories for as long as possible.