This species depends on rainforest and gallery forest; it is rarely found in degraded habitats, although sometimes occurs in secondary forests. Colobus polykomos usually forms small multi-male groups. In the Cantanhez Forest in Guinea-Bissau, groups consisted of 3–10 individuals, while at Tiwai Island Wildlife Sanctuary in Sierra Leone, one habituated group had nine members (Dasilva 1989). Lone individuals have also been observed. At Tiwai, it associates with the Western Red Colobus (Piliocolobus badius badius). Mean group size of the Taï population is 15 (range 12–19) (Korstjens 2001, Zuberbühler and Jenny 2002). In Mt. Nimba, Liberia, it associates with the Diana Monkey (Galat and Galat-Luong 2000). Low mtDNA diversity indicates that female philopatry and male dispersal is common in this species (Minhós et al. 2013). Dasilva (1994) studied the diet of C. polykomos in the mid-1990s at Tiwai and found that 30% of feeding time was spent eating leaves and seeds. In Taï, this species is more frugivorous than the sympatric red colobus and Olive Colobus monkeys (Korstjens et al. 2007).

Colobus polykomos can live in high altitude areas. Individuals were observed at montane areas at 673–1,061 m in the Fouta Djallon region in Guinea (C. Alonso and A. Hernansaiz pers. obs. 2014).

Colobus polykomos is listed as Class A under the African Convention and under Appendix II of CITES. It is found in a number of protected areas, including Sapo National Park (Liberia), Grebo-Krahn National Park (Liberia), Gola National Park (Liberia), Gola Forest National Park (Sierra Leone), Loma Mountains National Park (Sierra Leone), Tiwai Island Wildlife Sanctuary (Sierra Leone), Taï National Park (Côte d'Ivoire), and Cantanhez National Park (Guinea-Bissau). Rigorous law enforcement against poaching in protected areas is needed to ensure the survival of this species; permanent research stations in protected areas would greatly assist conservation efforts.

Although C. polykomos is found at very low densities in many of the forests where it still occurs, accurate estimates of the size and density of these populations are needed. Systematic surveys should be conducted in Grebo-Krahn NP in Liberia, Gola Rainforest NP and Loma Mountains NP in Sierra Leone, Cantanhez and Dulombi NP in Guinea-Bissau. In Cote d'Ivoire, the Tai Monkey Project, Centre Suisse de Recherches Scientifiques en Cote d'Ivoire (CSRS) and the Wild Chimpanzee Foundation have been making efforts to conserve the primates of the Tai National Park for several decades.