Unlike most social media, the new platform BeReal encourages users to present an authentic self. Since such self-presentations are assumed to have positive effects, this study examined whether adolescents’ authentic self-presentations on BeReal relate to a higher self-esteem and whether self-concept clarity plays a role in that relationship. The relationships between exposure to perceived authentic self-presentations of others, social comparison on BeReal, and self-esteem were also explored. Of the 367 adolescents who participated in our cross-sectional survey, a total of 148 (40.33%, Mage = 16.23, SDage = 1.46; 82.4% girls) had an account on BeReal. Using structural equation modeling (SEM), we found that these adolescents’ authentic self-presentations were not significantly related to their self-concept clarity nor indirectly to their self-esteem. Self-esteem and self-concept clarity were, however, positively correlated. Regarding exposure to others’ content on BeReal, only upward and downward social comparisons on these platforms were significantly related to a lower and higher self-esteem, respectively.