Due to the COVID-19 pandemic, restrictive sanitary measures such as lockdowns have been implemented all around the world. Based on a representative sample of the population collected through an online cross-sectional survey, the goal of the study was to investigate the factors associated with lockdown agreement in France during the second general lockdown of fall 2020. More specifically, we aimed to investigate how trust in the government and COVID-19 conspiracy beliefs influenced lockdown agreement. Trust in the authorities and low adherence to conspiracy beliefs appeared as strong predictors of lockdown acceptance among our sample. Using a mediation analysis, we highlighted a significant indirect effect of trust in the authorities on lockdown agreement through the adherence to conspiracy beliefs: low level of trust translated into higher odds to believe in COVID-19 misinformation which in turn decreased lockdown support. The double effect of trust on lockdown agreement, both directly and indirectly, underlines the importance of careful communication from the government around decisions related to COVID-19 mitigation measures in order not to deteriorate even more the low level of trust in the health action of the government. The fight against false information also appears of the utmost importance to increase the population adherence to public authorities’ recommendations.