Type 1 diabetes (T1D) is a chronic condition affecting many adolescents worldwide. Active involvement in self-care, coupled with good school support, enhances treatment adherence and impacts quality of life. This study analyzed the psychometric properties of the Self-Care Inventory-Revised (SCI-R) and the Diabetes School Support Scale (DSSS) in Portuguese adolescents diagnosed with Type 1 Diabetes (T1D). The sample included 100 adolescents diagnosed with T1D, aged between 12 and 19 years old, and their accompanying family members. Adolescents were assessed on quality of life ( Diabetes Quality of Life), illness perceptions (Brief Illness Perception Questionnaire), family functioning (Family Assessment Device), adherence to treatment (Self-Care Inventory), and school support regarding diabetes (Diabetes School Support Scale). Exploratory factor analyses (EFA) and confirmatory factor analyses (CFA) were performed to analyze the adequacy of the instruments. CFA confirmed the one-factor model with good fit indexes. The instruments presented good convergent validity and internal consistency. The Portuguese versions of the Self-Care Inventory-Revised and the Diabetes School Support Scale are valuable tools for assessing Portuguese adolescents’ self-care and perceived school support in T1D. Patient-centered care that integrates school support recognizes the adolescent as an active partner in treatment, respects their need for normalcy and privacy, and addresses contextual challenges that may otherwise compromise adherence.