Increasingly, celebrities appear not only as endorsers for products but are apparently involved in entrepreneurial roles—as initiators, part owners and/or in managerial capacities—in the ventures that market the products they promote. We call this phenomenon Celebrity Entrepreneurship. Whether or not this type of involvement on the part of the celebrity is original and genuine, it may be suspected that celebrity entrepreneurs are more effective communicators than typical celebrity endorsers. This research hypothesizes that such is the case. Further, we hypothesize that this is because celebrity entrepreneurship leads to higher perceptions of a source’s Involvement—an endorser quality hitherto neglected in the marketing communication literature—which in turn affects traditional outcome variables such as Aad (Attitude toward the ad) and Abr (Attitude towards the brand). Based on two experiments using subjects from the relevant product target group (n=88 and n=77) we tested their reactions to advertisements containing the celebrity Cameron Diaz after exposure to one of three experimental conditions: entrepreneur; mere endorser, and no information (control). The results confirm that a) involvement can successfully be operationalized as distinct from variables previously shown to influence communicator effectiveness (trustworthiness, attractiveness and expertise), b) involvement has a positive effect on Aad and Abr over and above the traditional predictors and control variables, and c) the celebrity entrepreneur condition in the experimental manipulation leads to increased perceived involvement.