Many global norms are currently facing substantial contestation by various actors. While contestation is a regular practice in norm dynamics, it can potentially result in the destabilisation of norms. At the same time, international city networks (ICNs) are increasingly positioning themselves in global governance. While research in International Relations has not analysed how ICNs respond to norm contestation and whether they stabilise existing norms and normative orders, this article demonstrates that ICNs are relevant actors in norm dynamics by focusing on their activities. To examine how ICNs stabilise norms, we employ a theoretical framework based on existing approaches in norm research, which assumes that norms must be as robust, resilient and legitimate as possible to maintain their functions in facilitating individual orientation and collective order. Empirically, we analyse the stabilising activities of three ICNs – Mayors for Peace, Rainbow Cities Network and Fast-Track Cities Initiative – as contributions to preventing norm decay in security, human rights and health. We show that these ICNs stabilise norms by supporting them in discourse and practice, by connecting norms in clusters, and by including affected stakeholders. In sum, we present ICNs as relevant actors in global governance due to their stabilising activities and networked capacities.