Abstract
INTRODUCTION: This study examines how sports celebrities' personality traits-likability, expertise, credibility, and physical attractiveness-affect millennials' purchasing decisions across Instagram, Snapchat, and Twitter. Addressing a gap in prior endorsement research that often treats social media platforms as interchangeable, the study adopts a cross-platform perspective to investigate whether the effectiveness of celebrity traits varies by platform. METHODS: A mixed-methods approach was employed. Quantitative data were collected through a survey of 228 millennials using stratified random sampling, while qualitative insights were obtained from semi-structured interviews with 12 participants. The interviews explored motivations, engagement patterns, and factors contributing to endorsement effectiveness. The study was guided by Source Credibility Theory, the Elaboration Likelihood Model, the Cognitive Response Model, and the Attitude-Toward-the-Ad Model. RESULTS: The findings indicate that perceived product quality partially mediates the relationship between sports celebrities' personality traits and purchase intention. Moreover, the influence of each trait varies significantly across Instagram, Snapchat, and Twitter, suggesting that celebrity endorsement effectiveness is contingent on the social media platform. DISCUSSION: By explicitly comparing multiple social media platforms and integrating quantitative and qualitative evidence, this study advances endorsement research by demonstrating that celebrity trait effectiveness is platform-specific rather than uniform. While all examined traits shape consumer responses, their relative importance differs across platforms, highlighting the need for platform-sensitive endorsement strategies and careful selection of celebrity endorsers. This cross-platform, mixed-method perspective provides nuanced insights into how digital celebrities influence consumer behavior and offers practical recommendations for marketers seeking to optimize influencer strategies across diverse social media channels.