Background Health literacy (HL) plays an important role in shaping adolescent health, particularly during a developmental stage characterized by increasing autonomy and active engagement with health information. Nevertheless, Malaysia has limited validated tools specifically designed to assess HL among adolescents. The Health Literacy for School-Aged Children (HLSAC) instrument is a theory-driven, capability-based measure developed for school contexts and extensively applied in international research. Therefore, this study aimed to translate and culturally adapt the HLSAC questionnaire and to assess its psychometric properties among Malaysian adolescents.Methods This study employed a cross-sectional design, following internationally recognized guidelines for cross-cultural instrument adaptation. The research team translated the HLSAC questionnaire into Malay using a forward–backward translation procedure and subsequently evaluated translation validity through expert review and assessed face validity among adolescents. The study quantified content and face validity using the Content Validity Index (CVI), Content Validity Ratio (CVR), and Face Validity Index (FVI). Construct validity was examined using exploratory and confirmatory factor analyses (EFAs and CFAs) based on pilot data from 128 adolescents aged 13–16 years recruited from school-based settings in Selangor, Malaysia. The study assessed internal consistency reliability using Cronbach's alpha and McDonald's omega.Results The HLSAC Malay version demonstrated excellent content validity (S-CVI/Ave = 0.99) and strong face validity (S-FVI/Ave > 0.97). EFA supported a unidimensional factor structure, with all items showing acceptable factor loadings (0.46–0.69). CFA confirmed good model fit (CFI = 0.945; TLI = 0.930; RMSEA = 0.055; SRMR = 0.058). The scale demonstrated good internal consistency (Cronbach's α = 0.806; McDonald's ω = 0.809).Conclusions The Malay version of the HLSAC is a valid and reliable instrument for assessing health literacy among Malaysian adolescents. Its suitability for school-based administration supports its application in adolescent health research, population monitoring, and health promotion initiatives, while facilitating cross-national comparisons.