This paper addresses the question whether three distinguished types of motivation influence workers’ participation in formal and informal learning at work. We particularly focus on the differential effect of motivation on younger and older workers’ participation in learning activities. In terms of human capital formation, we account for workers’ job tasks as a potential mediating factor between motivation and participation in learning activities. Results show that younger workers are mainly motivated by intrinsic motivation or self-regulation, while older workers are mainly motivated by intrinsic motivation. Results suggest that creative, difficult job tasks are related to younger workers’ participation in both formal and informal learning, while for older workers job tasks are only related to informal learning participation. Furthermore, the mediating effect of job tasks is for younger workers strong for both formal and informal learning, while for older workers this effect only exists for informal learning. This suggests that the self-selection into jobs which require formal and informal learning, mostly occurs among younger workers, while the self-selection into jobs which require only informal learning occurs among both younger and older workers.