This paper contributes to the literature on social sustainability in urban governance, with a focus on how this concept may be integrated into a Smart City strategy, so that excessive enthusiasm for smart technologies does not lead to neglect of the social implications of certain policies or programmes. By relying on a case study-based analysis, this work explores the path followed by the municipal government of Milan, and shows that integration of social sustainability into the Smart City strategy can be pursued by focusing both on the ‘content’ and the ‘process’ of strategy building. Rather than playing a strong leadership role, the planning department on the internal front and the entire municipality on the external front have chosen a role based on co-creation with citizens and other relevant stakeholders. The benefits of this approach may include the bottom-up character of several projects, better responsiveness and greater opportunities for different categories of actors; the drawbacks may include greater difficulty in ensuring that certain objective are reached (e.g. in terms of fairness and representativeness) and a higher risk of the dispersion of resources. This case also points to the difficulty of assessing the social sustainability of multiple rather than individual projects and programmes combined in a Smart City strategy: projects may reinforce each other in their social impact, or otherwise hinder possible benefits; also, a municipality may choose a combination of smart projects and programmes that attach different weights to economic, environmental and social sustainability objectives.