Cercopithecus pogonias has a large range, estimated to cover about 1,108,230 km² of moist tropical forest and forest-savanna mosaic. It is found in Cameroon, Central African Republic (CAR), Congo, Democratic Republic of Congo (DRC), Equatorial Guinea (including the island of Bioko), Gabon and the Cabinda enclave of Angola. Hicks (2010) found that the species was abundant in Bili-Uéré, north of the Rubi River up to the border with CAR (Mbomu River). The northern limit of its distribution is probably the limit of high canopy forest to the north, between about 4° and 6° N, although some parts of the historic range are a little further north and are now degraded forest (if the species is still present). As far as is known, the eastern limit is at about 26° E. and then the right (north) bank of the Itimbiri River in DRC and the right (north) bank of the Congo River, down to the forest-savanna limits in Congo. It may overlap or abut with the distribution of Cercopithecus denti, but there is a lack of information from the possible overlap zone (Sarmiento and Kingdon 2013) and Hicks (2010) saw only C. denti in the bushmeat markets between the Uélé and Rubi Rivers (forest identifications could potentially have been confused with the very similar C. denti). To the southwest, it is possible that this species occurs all the way to the Congo estuary where suitable habitat remains and hunting pressure is low. 

Historically, this species was found in Cameroon (Takamanda National Park) at about 9.3° E; however, the most recent surveys in Takamanda (Ikfuingei and Kuchambi 2013) and Dimonika Reserve in Congo (Latour 2010) did not record it, so we must assume it is already extirpated or has become extremely rare in this region. Recent surveys across the Cross River region in Nigeria did not record C. pogonias (Imong et al. 2009), so the Cameroon-Nigeria border area is likely the present western limit.

There are three subspecies. The distribution of the nominate subspecies, C. p. pogonias is a little unclear. Gautier-Hion et al. (1999), restricts it to Bioko, Equatorial Guinea, with an unnamed subspecies replacing C. p. pogonias on the mainland north of the Sanaga River. However, Groves (2001) reports C. p. pogonias as occurring from the Cross River across the Sanaga River to Río Muni, and includes Bioko. In the current treatment, C. p. pogonias includes the animals on Bioko (ca 2,000 km²) and on mainland Africa in the moist forest region between Cross River State, Nigeria, where the Sanaga River in Cameroon marks its southeastern distribution limit (Oates 2011), totalling over 50,000 km².

Cercopithecus p. nigripes is found in Congo, Gabon and Cabinda. The Ogooué River in Gabon limits its distribution to the north, and the Congo River to the south. The western limit – where no river clearly demarcates its distribution – is the forest-savanna boundary in southern Congo. Its range is about 166,000 km².

C. p. grayi ranges from southern Cameroon (middle Sanaga River) east to CAR and south into Congo and DRC, north of the Congo River. It ranges as far eastwards as the Itimbiri River, north of the Congo River. Gautier-Hion et al. (1999) map this subspecies as occurring south to the mouth of the Congo River.

For more details on the different subspecies, see the subspecies assessments.

Cercopithecus pogonias is listed on Appendix II of CITES, Class B of the EU Wildlife Trade Regulations, and on Class B of the African Convention on the Conservation of Nature and Natural Resources. Nationally, it is on the list of partially protected species in Nigeria (Federal Ministry of Nigeria 2004). Hunting, sale and consumption of primates in Equatorial Guinea were banned by Presidential Decree in October 2007 (Republic of Equatorial Guinea 2007), although no specific taxon is mentioned in that law. In DRC, C. pogonias is on the partially-protected list (may be hunted with a permit) (Enerunga 2006). In Congo, it is on Annex III of the current law (“all animals not on Annexes I or II”), meaning that it can be hunted for food, but only using traditional methods, and not for commerce, transport away from the site where it was hunted (in other words to a different village or other area), and trafficking products of the species on Annex III are strictly prohibited (MEFDD 2011). Similarly, they are on Class C (may be hunted with a permit) in Cameroon and CAR (Central African Republic 1984, MINFOF 2006).

Hunting is banned in all national parks where C. pogonias occurs so, on paper at least, the species is protected in those areas. However, weak application of and poor compliance with the law outside protected areas (and inside some PAs) results in gun-hunting through most of its range. The taxon occurs in many protected areas including three World Heritage Sites: Lopé-Okanda (Gabon), the Sangha Trinational (Cameroon-CAR-Congo) and the Dja Biosphere Reserve (Cameroon).

The species' strongholds (in terms of large areas of suitable habitat and abundance of individuals) are in the forests of Gabon, especially the protected areas, plus the Dzanga-Sangha complex in CAR, the protected areas of southeastern Cameroon, and the national parks of Conkouati-Douli, Nouabalé-Ndoki and Odzala in Congo. Outside protected areas, these monkeys are likely to be increasingly rare, especially in areas with medium-to-high human population density and active logging.