<p>Non-suicidal self-injury (NSSI) in adolescents is a significant public health concern, with global prevalence estimates ranging from 22.9% to 60% among community samples and even higher rates among clinical populations. NSSI has been found to be closely related to various psychological factors, among which maladaptive perfectionism and internalizing symptoms are considered to be important risk factors. This study aims to investigate the relationship between maladaptive perfectionism, internalizing symptoms and NSSI in adolescent psychiatric outpatients and consider resilience as a protective factor. The research was carried out within the psychiatric units of three medical facilities located in Hubei Province, China, and comprised 212 adolescent outpatients receiving psychiatric care (including 138 females, aged 12 to 19 years, <i>M</i> = 15.1, <i>SD</i> = 1.51). All participants completed the Ottawa Self-Injury Inventory (OSI), Youth Self Report (YSR), Chinese Frost Multidimensional Perfectionism Scale (CFMPS), Adolescent mental resilience scale, and socio-demographic scale. Results indicated that maladaptive perfectionism was positively associated with the frequency of NSSI(<i>r</i> = .28, <i>p</i> &lt; .01). Internalizing symptoms mediated the relationship between maladaptive perfectionism and NSSI (<i>β</i> = 0.02, 95% CI [0.01, 0.02]). Moreover, resilience was found to be a moderator between internalizing symptoms and the frequency of NSSI(<i>β</i> = -0.79, 95% CI [-1.25, -0.32]). These findings suggest that maladaptive perfectionism may be associated with higher NSSI risk through its relationship with internalizing symptoms, while resilience appears to be related to a weaker association between internalizing symptoms and NSSI behavior.</p>