In multiple brand endorsements (MBE), celebrities serve as endorsers for different brands simultaneously, which can be attractive for firms. Prior research has focused exclusively on how the number of simultaneously endorsed brands, such as MBE versus single brand endorsements, influences consumer behavior. This research instead analyzes drivers of MBE success, measured as brand attitude and brand purchase intentions, when a firm prefers MBE. Using a brand alliance perspective, this study accounts for spillover effects among brands connected through a celebrity and investigates four potential drivers of success: attitude toward the celebrity, familiarity of co-endorsed brands, attitude toward the co-endorsed brands, and fit between the co-endorsed brands. The empirical results from a consumer survey show that a brand can benefit from other brands’ involvement in an MBE. In addition, the findings empirically confirm a positive impact of brand fit on MBE success.