Backgrounds <p> This study explores the relationship between cyberbullying, mental health, and sexual minority groups, focusing on the specific impact of cyberbullying on these individuals’ mental wellbeing. Previous research has indicated that sexual minorities face higher levels of cyberbullying on social media. Therefore, this study aims to gain deeper insights into the mental health consequences and potential mitigating factors for this vulnerable population.</p> Methods <p>We employed a questionnaire survey method and convenience sampling to collect data. Participants’ psychosocial traits were assessed using established scales measuring stress, anxiety, depression, cyberbullying, loneliness, and sleep quality. Data analysis included Propensity Score Matching (PSM) and causal mediation analysis.</p> Results <p>Of the participants, 204 identified as belonging to sexual minority groups, constituting 7.1% of the overall sample. The correlation results indicated that individuals in the sexual minority group experienced higher levels of cyberbullying (<i>r</i> = 0.276, <i>p</i> &lt; 0.001). Cyberbullying was found to partially mediate the relationship between sexual minority status and several mental health issues, including depressive symptoms (0.32, 95% CI 0.19–0.53; <i>P</i> &lt; 0.001), anxiety symptoms (0.52, 95% CI 0.30–0.88; <i>P</i> &lt; 0.001), and loneliness (0.40, 95% CI 0.23–0.69; <i>P</i> &lt; 0.001). Additionally, cyberbullying fully mediated the relationship between sexual minority status and both stress and sleep quality.</p> Conclusion <p>These findings highlight that cyberbullying serves as a significant mediator in the mental health challenges faced by sexual minorities.</p>