Five studies assessed the validity and reliability of the connectedness to nature scale (CNS), a new measure of individuals’ trait levels of feeling emotionally connected to the natural world. Data from two community and three college samples demonstrated that the CNS has good psychometric properties, correlates with related variables (the new environmental paradigm scale, identity as an environmentalist), and is uncorrelated with potential confounds (verbal ability, social desirability). This paper supports ecopsychologists’ contention that connection to nature is an important predictor of ecological behavior and subjective well-being. It also extends social psychological research on self–other overlap, perspective taking, and altruistic behavior to the overlap between self and nature. The CNS promises to be a useful empirical tool for research on the relationship between humans and the natural world.