Mental health literacy (MHL) grows in importance as the prevalence of mental health conditions rises worldwide. There is a need for valid MHL measures especially among adolescents. The current study aims to develop and validate a Universal mental health literacy scale for adolescents (UMHL-A), a self report scale to assess MHL of children between ages 10 and 14 across all four components within Kutcher's framework for MHL. The development of the UMHL-A was initiated by a literature review and followed by item generation. Then, we tested the face and content validity of the scale via a delphi study, focus groups and cognitive interviews with the target group. Next with a convenience sample, we established the factor structure and construct validity of the scale using exploratory and confirmatory factor analyses. Lastly, we tested the scale convergent validity with other measures. The final form of the scale was refined on a representative sample of Czech asolescents. The UMHL-A scale comprises 17 items measuring four components of MHL. The scale has substantial methodological advantages in comparison to existing measures of MHL, especially considering its brevity and comprehensive coverage of MHL. Further studies are needed to test its application and validity globally.