Demographic changes increase the age range in occupational teams, which has potential consequences for collaboration not only at the team level (age diversity) but also at the individual level regarding how much effort workers expend. By integrating a life span perspective into theories on effort expenditure in teams, we assumed that workers’ chronological age moderates the relationship between task-specific self-efficacy beliefs and effort expenditure in organizational teamwork. More specifically, we assumed that task-specific self-efficacy beliefs are more strongly related with effort for older as compared with younger team members. Hypotheses were tested in 2 online studies (N = 209 and 271 workers, respectively) using the event reconstruction method. Participants were instructed to reexperience specific work events from the last few days (Study 1: 2 teamwork events; Study 2: 1 teamwork event and 1 working-alone event) and to indicate their self-efficacy and effort expenditure in each event. Results of both studies showed the expected age moderation of the self-efficacy–effort link in team settings, whereas no such moderation was observed in working-alone settings in Study 2. Finally, Study 2 also showed a stronger age moderation effect in unfamiliar as compared with familiar tasks.