This study provides a quantitative summary of the relationship between celebrity endorser source effects and effectiveness in advertising. The Kruskal-Wallis nonparametric test is used to identify the most influential celebrity endorser source effects on effectiveness. The role of celebrity/product fit, interaction effects, sample type, study setting, and country of study are also included as moderators. Results suggest negative celebrity information can be extremely detrimental to an advertising campaign. The source credibility model composed of celebrity trustworthiness, celebrity expertise, and celebrity attractiveness appears to capture the three most influential source effects on purchase intentions, brand attitudes and attitudes towards the advertisement.