In this chapter, we analyse the evolution of expert discourse in the media during the first wave of the COVID-19 pandemic in Canada. We begin with an overview of the use of expertise in the Canadian public-health decision-making chain in the context of the COVID-19 pandemic, highlighting the tensions, contradictions and paradoxes of political communication that this process revealed. These decisions were widely reflected and debated in the media, hence the relevance of studying them from the perspective of social representations. Based on our analysis of 527 media products published by CBC/Radio Canada between 1 January and 31 August 2020, it was possible to document the type of expertise mobilised, the types of experts engaged by the media, the modalities of appropriation of this discourse by non-experts and the use of expert discourse by political actors. The analysis of the governmental measures that have generated the most controversy and debate in the media has allowed us to reveal the public’s understanding of the pandemic through the process of representational naturalisation. Specifically, we show the role of expert discourse in determining which aspects of COVID-19 pandemic the public and political authorities in Canada have defined as a social problem.