Abstract In looking at the complex relationship between expertise and power in policymaking, what is amiss are studies on how the expertise exchange bargain between politicians and bureaucracy works in practice, especially in antidemocratic contexts. To deal with this limitation, we use Christensen’s (Christensen, J. (2022). When bureaucratic expertise comes under attack. Public Administration) expertise bargain change model for examining the authority transaction between politicians and bureaucrats. Upon external shocks, such as democratic backsliding with the sidelining of policy advice, the extant expertise bargain is challenged. We explore how the bureaucracy acted toward the government’s adversarial (and even antagonistic) stance and how that relationship toward the expertise bargain changed in two policy areas in Brazil (health and environment) during Bolsonaro’s administration (2019–2022). Notably, this article relies mainly on qualitative data from in-depth interviews with bureaucrats who provided expertise to the government on these policy areas during the Bolsonaro administration’s transition. Ancillary documentary sources were examined to detail the strategies of attack from government toward bureaucratic expertise and ancillary documentary sources of quantitative data from a survey with bureaucrats fielded during the Bolsonaro administration’s first year. Results show three factors that condition bureaucratic expertise’s resilience: the nature of the attack (local or extensive), the knowledge base’s and epistemic community’s level of cohesion, and the advice system’s degree of institutionalization. This case study sheds light on how different policy advice arrangements respond and function under antidemocratic contexts, allowing the application and enrichment of policy expertise literature outside regular democratic politics.