Abstract There have been conflicting findings about whether mandatory versus voluntary training leads to more positive training outcomes. We propose moving away from a dichotomous distinction to a more dynamic participation approach to better elucidate theoretical differences relating to self-determination theory. A sample of 311 trainees from eight companies participated in a variety of open skill (e.g., leadership) training programs. Results indicated that higher levels of voluntary participation were positively related to trainees’ transfer motivation and training transfer. We also found that the level of voluntary participation moderates the relationship between supervisor support and both motivation to transfer and training transfer. Supervisor support facilitates trainee motivation and transfer to a larger extent when participation is less voluntary. Future training should be framed and promoted to increase employee motivation to voluntarily participate, especially for employees with less supervisor support.