This paper discusses the theoretical relations between two emerging constructs for the prediction of human pro-ecological behaviour, and their role for the formation of prosustainability lifestyles: Affinity Towards Diversity (ATD) and Connectedness With Nature (CN). ATD is defined as an individual predisposition to appreciate the dynamic variety of human-nature interactions in everyday life situation. It is posited that ATD goes beyond a mere superficial acceptance for variation in social and physical contexts. Rather, it assumed that ATD implies the deep enjoyment and positive evaluation of the diversities existing in the surrounding environment, at both the biological and socio-cultural level. CN has been defined as an individual trait related to feeling emotionally connected to the natural world (Mayer & Frantz, 2004). Measures of CN have been found to moderate the state of well-being in nature-related leisure time activities in general (Röderer, Huber & Cervinka, 2009). The theoretical relations between these two construct are addressed in the light of the increasing importance that biological and social ecological sciences are assigning to the conservation of biological and cultural diversity within ecological systems, for the pursuit of sustainable development goals. The results of an empirical study on the role of ATD as a psychological driver of pro-sustainability orientation and pro-environmental friendly behaviours are presented and discussed. The study involved 390 participants, balanced for the main socio-demographic characteristics, living in four medium-small size Italian cities (with an average population of 50,000 inhabitants), located in central (Latina and Formia) and southern Italy (Salerno and Taranto). Participants were administered a self-reported paper-and pencil questionnaire, measuring the following variables: Affinity towards diversity; Altruism; Intolerance; Future orientation; Feelings of indignation for others’ anti-environmental actions; Positive and negative attitudes towards urban green; Proenvironmental behaviours. Structural equation model with latent variables (SEM) was used to test the hypotheses that ATD, together with the other variables considered, constitute a more general pro-sustainability orientation ( a second order factor), and that this, in turn, predicts pro-environmental behaviour. Results showed a good fit for the model tested (NNFI= .92, CFI = .93; RMSEA = .06). As expected, significant factor loadings between the first-order latent factors and their corresponding observed indicators were detected, suggesting convergent validity of the measures. The relations between pro-sustainability orientation and its predictors (the first-order latent variables) were also significant. All the factors considered emerged as direct predictors of pro-sustainability orientation (except for intolerance). In line with the hypotheses, pro-sustainability orientation showed a strong and significant relation to self- reported pro-environmental behaviours. The practical implications of these results for the relations between ATD and CN, and for the promotion of sustainable lifestyles are discussed.