The aim of the present study was to investigate the factors that influence volunteers to become involved in environmental action. The research focused on volunteers undertaking action in summer camps organised by an environmental non-governmental organisation (NGO) in Greece. The results suggest that the environmental issues addressed in volunteer programmes and the standards of volunteer organisations constitute critical predictors of a volunteer's personal commitment to participation in an organisation. Learning and contact with nature clearly emerged as the most important factors in volunteer motivation. Furthermore, although the participants considered their environmental knowledge was sufficient to stimulate their action, they also recognised the importance of continuing to deepen that knowledge. Most of the volunteers had participated previously in environmental education (EE), but only a few considered this experience to have influenced their intention to undertake action. Finally, volunteers seemed to believe in the power of citizenship and expressed a high internal locus of control. The findings of this study could enhance NGOs' understanding of what motivates volunteers and help them improve the quality and effectiveness of their volunteer programmes. EE practitioners could also use these findings to provide people with the proper capabilities to become consciously involved in voluntary environmental action. (Contains 1 note, 11 tables, and 1 figure.)