We investigated direct experiences with nature and socialization as predictors of preschool-aged children's environmental moral reasoning. Children (n = 146; 52.7% male) from three U.S. states completed biophilia and environmental moral reasoning interviews. Parents (n=98) completed surveys about their children's activities in natural areas and their valuing nature experiences. Most children (n = 140, 89.3%) judged throwing trash in a lake as wrong, even if everyone did it (n = 127, 92.9%) and even if it was far away where a rule permitted it (n = 137, 78.1%). "Harm to nature" and "anthropocentric" reasons were children's most frequent justifications. Children's access to a variety of natural areas and their nature knowledge significantly predicted environmental moral reasoning in stepwise multiple regression analysis controlling for demographic factors (F[subscript (5, 57)] = 3.8, p = 0.005), accounting for 19% of the variance. Parents' valuing nature experiences and children's biophilia did not significantly predict children's environmental moral reasoning.