This research aims to explore the role of brand personality self‐congruity (BPC) in affecting consumers' purchase behavior in a particular setting: video‐based social media (i.e., TikTok). Moreover, we test the moderating role of consumers' emotional attachment to the influencer and the mediating role of brand engagement in affecting purchase intention. Finally, we delve into the antecedents of influencer effectiveness and their relationship with consumers' actual purchases. To do so, we leverage two quantitative studies (n1 = 248; n3 = 247) and a qualitative one. Results from Study 1 indicate that the lower consumers perceive the gap between the brand personality and self‐image, the more they are inclined to engage with and purchase a brand. Moreover, we find that the emotional attachment to the influencer does not play a role in influencing purchase intention, positing that emotional attachment and BPC have different emotion dynamics with different purchase outcomes. Building on Study 1, Study 2 leverages a focus group to identify the antecedents of influencer effectiveness. Results highlight that a sense of indulgence appears in the minds of consumers when confronted with brands that have a lower congruity with their self. This sense of indulgence, in the case of low BPC, hinders the ability of the influencer to create an engagement between the brand and the consumer. Finally, Study 3 quantitatively tests the antecedents of influencer effectiveness under two conditions (entertaining vs. informative content type) highlighting the different influence of the antecedents on individuals with high (vs. low) BPC.