Prior research has focused on individual difference variables that predict various prosocial behaviors. This work, however, has neglected to consider the underlying commonalities between the different domains behavior can be performed. In line with other authors we propose that individual difference factors can indicate one's propensity toward acting prosocially across domains, and that prosocial behaviors also include behaviors that support behavior for the common good. We argue that in order for one's prosocial propensity to be actualized in a particular domain, a motivator in the form of connectedness to the domain is necessary. This paper examines such a model exemplified in the ecological domain by explaining pro-environmental actions. Through two studies (total N = 760) we provide evidence for a mediation model whereby connectedness to nature mediates the positive relation between prosocial propensity and pro-environmental behavior. Prosocial propensity was operationalized as altruism (studies 1 and 2) and honesty-humility (study 2). Further, study 1 also showed a comparison between participants indicating membership in environmental and humanitarian organizations and non-members. This indicated that prosocial propensity was higher in environmentalists and humanitarians compared to non-members, while connectedness to nature and pro-environmental behaviors were higher only in environmental organization members. These studies provide evidence for the premise of a prosocial propensity being actualized in the ecological domain via connectedness to that domain.