The research examines how consumer perceptions of brand marketing communications influence brand authenticity. During the COVID-19 outbreak, most industries experienced the negative consequences of the pandemic. However, the FMCG market in Indonesia continues to grow and is not negatively affected by the pandemic. One example is the increase in milk purchases which can be seen from the panic buying phenomenon of a milk brand in 2021. People aggressively buy milk products because they believe that the product can cure COVID-19. Hence, the authors chose a specific milk brand as the object of research. The authors investigated the direct effects of brand marketing communication on brand authenticity as well as the mediating effects of clarity of positioning. In addition, the authors analyze by controlling other marketing mix variables. This research uses a quantitative approach with a total of 326 respondents. The data is analyzed using Partial Least Squares-Structural Equation Modeling (PLS-SEM). The results of this study imply that there is a direct positive influence from brand marketing communications and an indirect influence through the clarity of positioning that can affect brand authenticity. Then, from all marketing mix variables, only brand satisfaction, price deals, and price images show the effect on brand authenticity. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.