The phenomenon of social loafing has been shown to be detrimental to group productivity. The present research examined social loafing in the context of team sports, while also providing an investigation into the validity of the Collective Effort Model (CEM) from within this framework. Participants were members of established sports teams, and were required to perform a running task individually and as a member of a relay. Situational variables were manipulated such that participants performed under conditions of low or high identifiability and low or high task valence. The results revealed support for the robustness of the social loafing and its generalisability to the domain of team sports. Furthernore, partial support was demonstrated for the CEM. These findings and their implications were discussed in terms of their relevance to the existing body of social loafing literature and group process theory in general.