Introduction: Personality and trust have been found to be important precursors of information-sharing behaviour, but little is known about how these factors interact with each other in shaping information-sharing behaviour. By integrating both trust and user personality into a unified research framework, this study examines how trust mediates the effect of personality traits (specifically, agreeableness and conscientiousness) in triggering information-sharing behaviour in an online social networking environment. Method: Integrating the Big Five theory of personality and the theory of generalised trust, a research framework is proposed for the determinants of information-sharing behaviour on social media. Data about personality, trust, and information sharing were collected from Chinese youths through an online survey. Analysis: Structural equation modelling was applied to data from 311 valid questionnaires to verify the research framework. Results: Both personality traits and generalised trust have a significant impact on information-sharing behaviour on social media, and generalised trust plays a mediating role between personality traits and information-sharing behaviour. Conclusion: This research advances the understanding of why information is shared within social media contexts with regards to trust and personality traits. It also clarifies the connections between personality traits, information-sharing behaviour on social media, and generalised trust.