Background <p>Adolescent smartphone addiction is a growing public health concern that negatively impacts mental health and daily functioning. The Smartphone Addiction Scale -Short Version (SAS-SV), developed by Kwon and colleagues, is a widely validated measure used globally to assess this issue. However, a psychometrically sound Tamil version suitable for adolescents has been lacking. This study aimed to translate SAS-SV into Tamil, evaluate its psychometric properties, and assess measurement invariance across genders.</p> Methods <p>The translation followed internationally accepted cross-cultural adaptation guidelines. Cronbach’s α and McDonald’s ω were used to measure reliability. The study employed Confirmatory Factor Analysis (CFA) to assess structural validity and Multigroup CFA (MGCFA) examined measurement invariance across gender.</p> Results <p>Internal consistency for the SAS-SV-T is good (Cronbach’s α = 0.83 and McDonald’s ω is 0.83). The CFA results indicated standardized factor loadings of 0.49 to 0.61, supported by a unidimensional structure. The model fit was acceptable with χ²(df) = 58.7(34), <i>p</i> =.01; CFI = 0.98; TLI = 0.97; RMSEA = 0.04; SRMR = 0.03. The scale also showed full measurement invariance across gender.</p> Conclusion <p>A valid and reliable measure of smartphone addiction in Tamil-speaking adolescents is the SAS-SV-T. Measurement invariance across gender supports its use in both research and clinical practice. This study fills a gap in adolescent health and addiction research by offering a culturally relevant instrument.</p>