The social organization of the kinkajou Potos flavus is described from 380 h of observations on habituated, free-ranging animals. Individuals were most often alone while feeding at night, yet they regularly interacted in stable social groups. Four social groups were observed, each consisting of a single adult female, two adult males, one sub-adult and one juvenile. At least one breeding female was solitary and did not reside within a group. Social groups were consolidated primarily at denning sites and large fruiting trees by group feeding, allogrooming and scent marking. However, kinkajous were most often observed solitarily, as social feeding only occurred in 19.6 of total feeding bouts (mainly among males) and individuals rarely travelled together. Although the composition of social groups was polyandrous, males also copulated with non-group females which suggests a promiscuous mating system. Female-biased dispersal and patterns of male association seem to be patrilineal and based on resource defence. The evolution of social organization in the kinkajou is discussed in relation to predation risk, resource availability, and convergence with primates of similar fission–fusion socioecology.