The relationship between the city and “innovation” is long and varied, but in recent years there has been a new focus on the potential of innovation to catalyze economic, social, and environmental change. This has led to a debate around whether and how innovation might be progressive, and the extent to which it is captured by–indeed driven by–neoliberal thinking and processes. Our argument is that a useful route to understanding and evaluating the forms and politics of innovation in the city lies in critically examining how the “urban”, the “social”, and “innovation” are differently understood, put to work, and brought together by different actors. Exploring how these terms are relationally co-constituted is different to existing approaches. We do not seek to identify principles of what makes good urban social innovation, and we go beyond separating out different cases as “neoliberal” or “progressive” (though we keep a hold of that critical focus). We show that a relational focus enables an understanding of the constitutive elements through which “urban social innovation” differently proceeds. This approach can help nuance, diversify and broaden how we understand the forms and potentials of initiatives presented to us as “urban social innovation”.