Research Question: The current study examined the role of signalling and source credibility on athlete-related social media content. We examined the effect of three different posting sources on sport consumer perceptions of athlete brand image and social media engagement with athlete-related content. Research Methods: Data were collected via an online experiment which presented information about an athlete to three groups. Group one received the content direct from the athlete, whereas group two and three saw the same content presented by indirect sources (the athlete’s team and a news media outlet). In total, 315 consumers participated in the experiment. ANCOVA and MANCOVA tests were used to test the hypotheses. Results and Findings: In general, sport consumers possessed more favourable attitudes towards athlete content on social media when it was presented by an indirect source. This content was perceived as more credible and less biased than when the same information was sent from the athlete directly. Results demonstrated some evidence consumers’ intentions to engage with athlete-related social media content were greater when this content was posted by an indirect source, rather than directly by the athlete. Implications: This research contributes to knowledge guiding athlete brand development via social media. Athletes need to be aware that not only the type of content posted about them influences consumer perceptions about their brands, but so too does the source of the content. To build their brands effectively and to elicit engagement, athletes should collaborate with credible and trustworthy third-party organisations when communicating via social media.