Existing co-branding and brand extension research generally coalesces around two important constructs: perceptual fit and attitude toward the brand. Studies in co-branding and brand extension to date have generally emphasized the transference of affective elements of attitude from parent brand to the extension. Researchers and practitioners clearly need to learn more about the transfer of belief, the cognitive elements of attitude. Too little is currently known about whether and how beliefs are actually transferred in co-branding and brand extension applications, particularly in terms of perceptual fit. This dissertation investigates belief transfer and the effect of perceptual fit on belief transfer in co-branding and brand extension scenarios and develops answers to the following research questions: 1.Are different categories of beliefs transferable from parent brand to theextension? 2.How do various sub-dimensions of perceptual fit affect belief transfers fromparent brands to the extension? 3.How do different categories of beliefs affect consumers’ intentions to purchasethe extension products? Categorization Theory was used as the fundamental theory to build the hypotheses. This dissertation involved qualitative studies, belief scale development, and experimental design studies. The results revealed that aesthetic and functional beliefs are positively transferred from parent brand to the extension. The transfer of aesthetic beliefs is affected by the level of brand fit while the transfer of functional beliefs is independent upon the level of any perceptual fit construct. Finally, cognitive structure based on the strength of extension beliefs is more predictive upon the purchase intention. Findings will extend the co-branding and brand extension literature, especially in terms of the pattern of belief transfers that unfold subject to the influence of various perceptual fit constructs. The results will also provide additional insights about the role that perceptual fit plays in influencing categories of consumer beliefs as those beliefs are also influenced by the specific perceptual fits that are presumably transferred to the extension.