PURPOSE: This study aims to examine the relationship between loneliness and hopelessness and mobile phone addiction (MPA) in non-suicidal self-injury (NSSI) adolescents, exploring the mediating role of problem-focused and emotion-focused coping. METHODS: This cross-sectional study recruited a total of 1545 NSSI adolescents and 553 non-NSSI adolescents from over 20 specialized psychiatric hospitals across multiple provinces in China. The participants were asked to complete the Beck's Hopelessness Scale, UCLA Loneliness Scale, Coping Style Scale, and Mobile Phone Addiction Index questionnaire. We mainly used the -tests and structural equation model to analyze the data. RESULTS: -tests showed that NSSI adolescents had lower scores on problem-focused coping and higher scores on MPA, loneliness, hopelessness, and emotion-focused coping than non-NSSI adolescents. Structural equation model showed that loneliness and hopelessness were positively related to MPA for non-NSSI adolescents. Hopelessness was positively related to MPA for NSSI adolescents. Emotion-focused coping played a mediating role in the relationship between loneliness/hopelessness and MPA for both NSSI and non-NSSI adolescents. CONCLUSION: These findings suggest that NSSI adolescents with loneliness and hopelessness may have mobile phone dependence, highlighting the mediating role of emotion-focused coping style. Such findings help to understand the formation mechanism of MPA for adolescents with NSSI. Alleviating the loneliness and hopelessness and improving adaptive coping styles of adolescents with NSSI have potential implications for reducing their MPA.