Objective: To investigate the mediating effect of insomnia among mobile phone addiction, aggressive behaviors and self-perceived identity among university students. Methods: A total of 740 university students were sampled from five universities in Binjiang District, Hangzhou City using a cluster random sampling method. The mobile phone addiction, aggressive behaviors and self-perceived identity were assessed using the Mobile Phone Addiction Index Scale, the Athens Insomnia Scale, the Chinese college students' version of the Buss-Perry Aggression Questionnaire, and the Self-Perceived Identity Scale, and the mediating effect of insomnia among mobile phone addiction, aggressive behaviors and self-perceived identity was examined using Process macro program and Bootstrap method. Results: A total of 740 questionnaires were allocated, and 700 valid questionnaires were recovered, with an effective recovery rate of 94.59%. The respondents included 221 men (31.57%) and 479 women (68.43%), and there were 607 respondents with a specialty of medicine (86.71%). There were 331 participants detected with mobile phone addiction (47.29%), 90 with aggressive behaviors (12.86%) and 289 with low-level self-perceived identity (41.29%), and the prevalence rates of mild, moderate, severe and extremely severe insomnia were 28.00%, 26.14%, 26.43% and 19.43% among respondents, respectively. Mobile phone addiction had a direct predictive effect on aggressive behaviors (β=0.301, P<0.001) and self-perceived identity (β=-0.129, P<0.001), and presented an indirect predictive effect on aggressive behaviors (effect of mobile phone addiction on insomnia: β=0.083, P<0.001; effect of insomnia on aggressive behaviors: β=0.999, P<0.001; effect of insomnia on self-perceived identity: β=-0.698, P<0.001). The contributions of mediating effects caused by insomnia were 21.61% and 31.02% to total effects. Conclusions Insomnia presents partial mediating effects among mobile phone addiction, aggressive behaviors and self-perceived identity among university students. Mobile phone addiction may directly affect aggressive behaviors and self-perceived identity, and indirectly affect aggressive behaviors and self-perceived identity via insomnia.