Although national disaster risk reduction policies in Argentina are still incipient and fragmented, the city of Santa Fe managed to adopt flood-risk management strategies after a major flooding in 2007. This involved a shift from reactive measures to a proactive policy approach to manage one of the city's main problems. Employing insights from institutional theory, this paper explores and elaborates on the institutional conditions that enabled policy change in Santa Fe. A qualitative case-study design is used, and the analysis builds on previous empirical studies of Santa Fe, policy documents and in-depth interviews. Three institutional conditions were identified as fundamental contributors to policy change: place identity, policy publics, and practical authority. These conditions were used and developed by the new administration elected after the flooding. This paper argues that the new administration took advantage of the ‘legitimacy vacuum’ of the old administration, following from its passivity and reactive handling of the flooding. The new administration mobilized and strengthened pre-existing institutional conditions, and reconfigured power relations through its practical authority. Instead of a partisan strategy, the new administration expanded agency in terms of a community-based approach (collective action), expert knowledge, and problem-solving skills, which underscores the importance of informal institutions to complement and reinforce formal ones. This article provides lessons for local communities with similar conditions as the city of Santa Fe, showing that local actors can develop proactive disaster risk reduction also in unfavourable national contexts.