Purpose: This study examines the effect of irrelevant celebrity co-branding partner information presented in advertisements on consumer brand judgments. Brand unrelated information carried by a celebrity co-branding partner is arguably irrelevant to consumer judgment formation and perhaps more so when the image of the celebrity is incongruent with that of the brand. Originality: Irrelevant information presented by a well-known comedian, Jerry Seinfeld, in a current campaign with a financial institution, the Greater Building Society, may cause a weakening effect on consumer brand benefit beliefs, attitudes and purchase intentions. Key literature/theoretical perspective: The social and non-social judgment literature recognises that the use of irrelevant information results in less extreme judgements (dilution). Design/methodology/approach: A 2 x 4 experimental design manipulated information relevancy and celebrity-brand match-up. Findings: A dilution effect on consumer brand benefit beliefs, attitudes and purchase intentions was identified with the addition of irrelevant information provided by a celebrity co-branding partner. Results show that both information relevancy and celebrity-brand match-up influence consumer brand benefit beliefs and purchase intentions, whereas only match-up information is used in the formation of brand attitudes. An incongruent and irrelevant celebrity co-branding partner results in decreased consumer judgements compared to an irrelevant yet matched celebrity brand partner. Research limitations/implications: As this study focused on one television advertisement with a specific celebrity and co-branding partner, future research should be extended to explore other mediums and other co-branding situations. Practical and Social implications: Brand managers should strategically place a relevant celebrity co-branding partner, a congruent celebrity who presents relevant brand related information, within their advertisements to avoid brand benefit belief and purchase intent dilution.