Volunteering for nature conservation has become an important resource in solving local environmental problems of global importance. The study at hand assessed how well millennials` global citizenship attitudes explain their behavioral intentions to engage in volunteer projects, as well as how prior experience of volunteering in environmental projects affects millennials` global citizenship attitudes. Those who reported past participation in this type of volunteer experience were generally more inclined to partake in future environmental volunteering than those without prior experience. Likewise, for those with prior experience, global citizen factors played a greater role in intentions to experience environmental volunteering. This study makes valuable contributions to the literature surrounding nature conservation, as it illustrates that millennials` global citizenship attitudes predict participation in environmental volunteering. This work concludes with insights concerning what programs (that provide millennials with opportunities to fulfill environmental duties associated with their global environmental citizenship) can do to provide a more valuable experience for young volunteers.