We investigate whether partners in a brand alliance should be similar or dissimilar in brand image to foster favorable perceptions of brand fit. Using a Bayesian nonlinear structural equation model and evaluations of 1,200 brand alliances, we find that the conceptual coherence in brand personality profiles predicts attitudes towards a brand alliance. More specifically, we find that similarity in Sophistication and Ruggedness and moderate dissimilarity in Sincerity and Competence result in more favorable brand alliance evaluations. Overall, we find that similarity effects are more pronounced than dissimilarity effects. Implications for brand alliance strategies and marketing managers are discussed.