This article explores the effects of the COVID-19 pandemic on the practices of collective intervention and intersectoral action in Sherbrooke, in the province of Quebec, to understand the local dynamics during the health crisis. Semi-structured individual interviews were combined with document analysis. Data was analysed using thematic content analysis. Five main themes summarise the results. The processes of collective intervention and intersectoral action are characterised, before the pandemic, by a wellestablished collaboration culture, by deep-rooted consultations and by concerted practices; and during the pandemic, by agile response management, by resilient and creative practitioners and by a spontaneous definition of new roles adapted to the context. The proposed communication strategies focus on access sources and on understanding the information provided. Analysis of the effects of the pandemic reveals emerging needs and vulnerabilities that must be taken into account.