The paper investigates the psychological factors associated with the unprecedented assistance that Poles have offered refugees from Ukraine since the outset of Russia’s invasion of Ukraine. Building on social identity theory, and examining the current social context in Poland, we focus on three social identity dimensions, i.e., a feeling of closeness towards refugees from Ukraine, anticipatory fears (of a Russian invasion), and a community norm of helping. These three dimensions predict collective helping resulting from a sense of a common fate and a feeling of togetherness with Ukrainians. We tested this hypothesis in a study (N = 1066) conducted between 11 and 17 March 2022. Participants were asked about their helping activities during the previous week; they also responded to questions on different measures of social identity processes. The results support our expectations, revealing that closeness, anticipatory fears, and social norms are associated with two forms of help: benevolent and activist. The results of the study contribute to the discussion on social identity processes underlying offers of help to people fleeing from war-zones. Thus, they enhance our understanding of the role of citizens in terms of their contribution to helping refugees, and can be used to improve responses to other humanitarian crises.