This paper examines connections between childhood involvement with the natural environment and adult environmentalism from a life course perspective. Approximately 2,000 adults age 18-90 living in urban areas throughout the United States were interviewed with respect to their childhood nature experiences and their current, adult attitudes and behaviors relating to the environment. Model testing and cross-validation procedures using structural equation modeling suggest that childhood participation with nature may set an individual on a trajectory toward adult environmentalism. Specifically, childhood participation in “wild” nature such as hiking or playing in the woods, camping, and hunting or fishing, as well as participation with “domesticated” nature such as picking flowers or produce, planting trees or seeds, and caring for plants in childhood have a positive relationship to adult environmental attitudes. “Wild nature” participation is also positively associated with environmental behaviors while “domesticated nature” experiences are marginally related to environmental behaviors.