Incentives play an important role in human motivation (see Beckmann & Heckhausen, 2008). In the present research we used Rheinbergs (2008) distinction of activity-related incentives (e.g., having fun) and purpose-related incentives (e.g., improved fitness) and investigated the influence of these two types of incentives on commitment and well-being in the domain of sport. Assuming that activity-related incentives have stronger rewarding effects on human behaviour than purpose-related incentives, we hypothesized activity-related incentives to be stronger predictors of sport-commitment and well-being than purpose-related incentives. Study 1 (N = 129) confirmed this hypothesis using a correlational design. In Study 2 (N = 67) we experimentally induced activity- and purpose-related incentives. We found stronger effects of activity-related incentives on sport-commitment and well-being compared to purpose-related incentives.