Objectives <p>Self-harm behaviors among adolescents, including suicide attempts (SA) and non-suicidal self-injury (NSSI), present critical public health challenges globally. While past-oriented rumination and future-oriented hopelessness are established core dimensions of maladaptive self-cognition, their distinct associations with different forms of self-harm remain poorly characterized.</p> Methods <p>Using latent profile analysis, we investigated the heterogeneous profiles of rumination and hopelessness in a sample of 951 adolescents (M_age: 16.58; male: 420). We further examined how these latent profiles differ in their associations with SA and NSSI, controlling for general affective symptoms.</p> Results <p>Three distinct cognitive profiles were identified: high rumination–high hopelessness (<i>n</i> = 77, 8.09%), moderate rumination–moderate hopelessness (<i>n</i> = 531, 55.84%), and low rumination–low hopelessness (<i>n</i> = 343, 36.07%). Specifically, the high rumination–high hopelessness profile emerged as being uniquely associated with SA, even after controlling for affective symptoms. NSSI was related to the severity of depressive symptoms, but not related to the specific cognitive profiles.</p> Conclusion <p>Our study provides novel insights that the interaction between rumination and hopelessness generates distinct cognitive phenotypes, which show different associations with SA and NSSI. These findings address a key theoretical gap in self-harm mechanisms and suggest the need to reshape prevention paradigms by enabling phenotype-specific interventions targeting cognitive constrictions for at-risk youth.</p>