This paper investigates social identity and altruism in diverse teams. Past research identifies cooperative and altruistic behaviour as essential for team effectiveness. An important question concerns the extent to which individuals, as they interact with demographically dissimilar team members, will display altruism. This question is addressed drawing upon relational demography research and a social identity approach. The present study posits that identification with demographic subgroups within a diverse team is a major hurdle to attaining altruism. When team members identify with demographic subgroups, they are less likely to identify with the team and to engage in altruism. Using a sample of 221 individuals from 13 diverse teams, this study found that demographic identity salience was negatively associated with team identification and team identification was positively associated with altruism. Demographic identity salience was not related to altruism. This study examined fundamental but under-studied propositions of social identity approach within diverse team context.