Physical inactivity is a major public health challenge in the 21st century. Interventions to promote physical activity show too little success, meaning that a large part of the population still does not meet the recommendations for health-promoting physical activity. It is often argued that existing interventions to promote physical activity do not take enough account of affective processes during physical activity. It is still far too rare for people in interventions have positive exercise experiences (e.g., pride, interest, competence; Ekkekakis et al., 2021). In addition, interventions often do not empower individuals to direct their physical activity in ways that positively impact affective well-being and mental health (Sudeck & Pfeifer, 2016). The FEEL project addresses these deficits in research and practice. An exercise program to promote positive exercise experiences, competence for affect regulation, and affective well-being will be developed and evaluated using a randomized controlled trial.