Nature experiences are essential for fostering pro-environmental behavior. In this study, a wildlife observation toolbox was provided to students to encourage participation in nature observation clubs. A total of 340 adolescents joined the clubs. We identified the determinants of participation intentions with a mixed approach combing questionnaires and follow-up interviews. Nature connectedness and previous nature experiences were significant "push" factors for participation intention in nature clubs. No interest in plants and animals as "push" factor discouraged participation. This study highlights the importance of nature connectedness and makes another call for changing adolescents' environmental perception and access to nature.