This study sought to empirically investigate the causes of advertising confusion induced by similarities in advertising execution and appeal concepts in competitive advertising situations, as well as the effects of moderating variables on advertising confusion. In particular, this study focused on the similarity of advertising models and product category similarity as causes of advertising confusion, and on consumers' situational involvement with products and product knowledge as moderating variables. First, this study demonstrated that when the same model appears in product advertisements, consumers easily fall into a state of advertising confusion where they cannot link brands with advertisements. That is, the similarity of advertising models can be considered a powerful cause of advertising confusion, and these results show a degree of consistency with prior research on the negative effects of celebrity models' multiple endorsements on memory dimensions. Additionally, when competing brands use different advertising models, the study showed the preventive potential of product category dissimilarity against advertising confusion. Furthermore, the similarity of advertising models and product category similarity can operate independently to induce greater confusion, or in certain cases, reduce the likelihood of advertising confusion. Consumer product knowledge was verified as an effective moderating variable against the powerful advertising confusion caused by model similarity. That is, even when the same model appears in advertisements, if consumers possess high product knowledge, the likelihood of advertising confusion can be considerably constrained. Product category similarity induces greater advertising confusion in high-involvement groups compared to low-involvement groups. Specifically, high-involvement consumers may experience greater advertising confusion than low-involvement consumers when exposed to advertisements within the same product category. Synthesizing all these results, the similarity of advertising models is an extremely powerful cause of advertising confusion, and the confusion induced by model similarity can be effectively prevented by enhancing consumers' product knowledge or by evoking novelty and curiosity about the advertisement.