Existing attempts to explicate the impact of multiple-brand alliances on consumers’ perceptions have delivered contradictory insights: brand alliance researchers consider such impact as positive, while celebrity endorsement researchers conceptualize it as negative. This study addresses the reasons for this discrepancy by approaching persuasion knowledge theory. To test the hypothesized relationships, we conducted an experiment on 300 consumers, which explicated the negative impact of persuasion knowledge on consumer multiple-brand alliance advertisement attitude and post-alliance focal brand purchase intention. Empirical analysis revealed that consumer persuasion knowledge in brand alliances has a negative impact on purchase intention and focal brand attitude. Increasing the number of brand allies by one reduced the impact of persuasion knowledge and contributed to a stronger brand consideration.