With the concern of rainbow marketing, sexual minority travelers have become highly vigilant when evaluating hotels’ LGBT-friendly marketing with their authenticity. It is important to scrutinize how sexual minority guests interpret brand authenticity toward LGBT-friendly hotels and form personal meanings during their stay. For this reason, this study proposes brand authenticity as a starting point for authenticity formation, which leads to existential authenticity and brand loyalty. Confirmatory factor analysis and PROCESS analysis were used to analyze data collected from sexual minority guests who visited LGBT-friendly hotels within the last 2 years. The findings indicate that (1) brand authenticity is an antecedent to brand loyalty and (2) the relationship between brand authenticity and brand loyalty is mediated by existential (intrapersonal and interpersonal) authenticity. Thus, in building on the multifaceted concept of existential authenticity, this study adds new theoretical insight into hotel marketing and management strategies.