Due to its cryptic nature, the species is not well documented in all of its habitats but has shown unique traits, such as pair-bonding and aggressive behavior towards other guenons.

Locally known as swamp monkeys, these primates are named after the Italian naturalist and explorer Jacques Savorgnan de Brazza.

[3][4] Their scientific species name, neglectus, which means to pay no attention to, was given to them because of their ability to hide from both humans and predators.

Adults have grey agouti fur with a reddish-brown back, black limbs and tail, and a white rump.

Juveniles lack the darker colors on the extremities that is characteristic of adults, but retain the whites stripes and red rump while infants are a uniform brown agouti with only a small beard.

De Brazza's monkeys range across the swamps, bamboo and dry mountain forests of Angola, Cameroon, Central African Republic, Congo, Democratic Republic of the Congo, Equatorial Guinea, Ethiopia, Gabon, Kenya, South Sudan, Nigeria and Uganda and possibly Tanzania though reports have not been confirmed.

[8] The diet of De Brazza's monkeys consists mostly of herbaceous plants found on the forest floor, and fruits when available.

[7] Predators of the De Brazza's monkey include the crowned eagle, leopard, humans, and common chimpanzees.

[11] In some areas of Western Africa, such as Gabon and Cameroon, small pair-bonded groups of a male, female, and infants and juveniles have been observed.

This is unique because the species is not listed as vulnerable or endangered, but has been sponsored by the AZA to proactively prevent need for reactive conservation in the future.