The full extent to which non-human primates, including chimpanzees, cooperate with one another is widely debated [see Silk, 2005]. Accounts typically focus on cooperative hunting and intraspecific aggression [Boesch, 2003] or food sharing [Bethell et al., 2000], and the levels at which cooperative behaviours can be explained are numerous [e.g. Connor, 1995]. It is, therefore, important to document possible occurrences of such behaviours when they are observed, especially when these behaviours are displayed under more unusual circumstances. Here we report an event that occurred predominantly between an infant and adult chimpanzee and discuss this in terms of the competing theories underlying the evolution of cooperative behaviour (defined as an interaction that results in a net benefit to both parties [Trivers, 1985]) among social primates.