Background: Cyberbullying is a globally shared youth problem—a problem of the interpersonal conflicts and contradictions that emerge during the socialization of adolescents. In particular, the issue of cyberbullying among rural left-behind adolescents needs to be given high priority. However, previous studies have paid little attention to how emotional neglect and social anxiety affect the cyberbullying behavior of rural left-behind adolescents. Therefore, this study was based on cognitive-behavioral theory to investigate the relationship between emotional neglect, cyberbullying, and social anxiety. Methods: This study used the Emotional Neglect Scale, the Cyberbullying Scale, and the Social Anxiety Scale to conduct an anonymous online survey of 1429 rural left-behind adolescents in China. Results: (1) Emotional neglect, social anxiety, and cyberbullying showed a two-way positive correlation. (2) The direct effect of emotional neglect on rural left-behind youth cyberbullying was significant (β = 0.14,p< 0.00). (3) Social anxiety showed a partial mediating effect in the process of emotional neglect affecting rural left-behind youth cyberbullying, with a mediating effect of 26.32%. Conclusions: The results have positive implications for improving relevant policies and constructing mechanisms for protecting the rights and interests of rural left-behind adolescents.