In Europe, growing concerns about social segregation and social stability have pushed calls to make cities ‘inclusive, safe, resilient and sustainable’ higher on policy agendas. However, how to approach such generic policy objectives and operationalise them for planning practices is still largely unclear. This article makes a conceptual contribution to the operational understanding of social sustainability in urban planning practices. The article argues that, between theoretical concept and operational forms, different evaluative approaches towards social sustainability may be taken. Evaluating three dimensions of policy operationalisations in The Netherlands, we argue that Amartya Sen’s capability approach provides a promising conceptual framework for operationalising social sustainability in cities in Europe and beyond. We compare capabilities with a more commonly applied resource-based conception to show that the former is more accurate and potentially more effective, because it shifts the evaluative space of social sustainability from means (i.e., urban resources) to ends: the eventual well-being of urban citizens.