ABSTRACT This research investigated how identity fusion with environmental issues interacts with social norms to shape pro-environmental behaviors, elucidating the psychological structure underlying environmental ideological engagement. Building upon a measure of identity fusion that captures both relational and doctrinal components of Zmigrod ideology framework, we found that higher identity fusion positively predicted donations to an environmental association in a Dictator Game paradigm. Importantly, results revealed an interaction between identity fusion and norm source on donation amounts. For individuals lower in environmental identity fusion, pro-environmental norms had a greater impact when originating from a sourcesharing their worldview (low-fused) compared to a distant group (high-fused). However, for individuals with high fusion, norm source proximity did not significantly impact donations. By illuminating this interplay between the relational and doctrinal facets of ideological thinking, this research advances understanding of the social and psychological motivators of environmental actions. These findings highlight the importance of considering identity alignment and social dynamics in fostering ecological engagement.