Previous research has demonstrated that children take a strong moral stance toward protecting the natural environment. However, the question of how this moralization of pro‐environmental behavior develops in adolescence has been rarely investigated. This study investigated age‐related differences in adolescents' pro‐environmental behavior as it relates to moral judgments about environmental issues and emotions. The study was based on a cross‐sectional sample of 325 Canadian adolescents from early, middle, and late adolescence. It was found that older adolescents engaged less in pro‐environmental behaviors such as energy conservation and recycling. The effect of age was mediated by the prescriptiveness of moral judgment as well as emotional affinity for nature. The study calls for a systematic investigation of factors that suppress pro‐environmentalism in adolescence.