The Environmental Identity (EID) Scale was proposed by Clayton to study the relationship between identity and nature. Although it is cited in several publications, it has rarely been subjected to psychometric analysis. The main aim of this study is to analyze the fulfilment of construct and convergent validity criteria for this scale. For this purpose, 282 university students were asked to complete a questionnaire, along with related measures: Connectedness to Nature Scale (CNS), the Inclusion of Nature in Self (INS) scale, Ego-biocentrism and self-reporting of pro-environmental behaviours. Exploratory factor analysis of EID shows that there are four underlying dimensions: environmental identity; enjoying nature; appreciation of nature; and environmentalism. All the correlations between EID and the criteria variables were significant, with environmentalism and environmental identity as the best predictors of pro-environmental behaviour.