This study examined the effect of the audience’s similarity to, and parasocial identification with, spokespersons in obesity public service announcements, on perceived source credibility, and diet and exercise self-efficacy. The results (N = 200) indicated that perceived similarity to the spokesperson was significantly associated with three dimensions of source credibility (competence, trustworthiness, and goodwill), each of which in turn influenced parasocial identification with the spokesperson. Parasocial identification also exerted a positive impact on the audiences’ diet and exercise self-efficacy. Additionally, significant differences were found between overweight viewers and non-overweight viewers on perceived similarity, parasocial identification with the spokesperson, and source credibility.