The article argues that closer attention to how solidarity is understood and expressed in different European contexts can shed light on the conditions for establishing a social and solidarity economy. Drawing on data collected within the H2020 SOLIDUS project, which explores current expressions of European solidarity, the comparative analysis covers three social economy initiatives, each representing a country with different political and economic context. The analysis focuses on solidarity as reciprocity and, in particular, how it is affected by such factors as actor motivations, internal participatory functioning, resource mix and political legitimacy. While further empirical work is needed, the findings suggest that solidarity as reciprocity produced by social and solidarity economy organisations thrives where political institutions are both supportive and trusted, where public funding is accessible, and where partnerships with relatively autonomous social and solidarity economy organisations are genuinely collaborative.