Background: Mental health literacy (MHL) is especially important for young people, but comprehensive studies on MHL in adolescents are limited, with no nationwide studies in Spain. This research aims to study MHL among Spanish adolescents and its relationship with sociodemographic factors. Methods: An exploratory study is carried out using stratified random sampling in Spanish adolescents (N = 1000), aged 12–16 years and balanced in terms of gender, age and territorial distribution. Data collection took place in October and November 2023 through online surveys using the CAWI methodology. Sociodemographic variables, contact with mental health and the Spanish version of the Mental Health Literacy Questionnaire (MHLq-E), a self-administered instrument of 32 Likert-type items (1–5) that assesses the dimensions of help-seeking skills, knowledge about causes and symptoms, and stigma, were evaluated. Descriptive and multivariate analyses of variance (MANOVA) were conducted. Results: In general, adequate levels of literacy were observed, although some aspects related to help-seeking towards teachers, stigmatising attitudes towards people of low economic status and knowledge of severe mental health problems could be improved. The results show contact with previous mental health problems as a key variable for stigma and knowledge about symptomatology together with age. Likewise, gender and family educational level were found to be related to the ability to seek professional help. Conclusion: This study provides information on levels of MHL among Spanish adolescents and highlights significant socio-demographic variables. These findings pave the way for interventions aimed at improving adolescents' understanding, attitudes and skills to manage mental health problems, making possible to adapt content and focus on specific groups, thus increasing its effectiveness.
