Abstract Introduction: The strengths and difficulties questionnaire (SDQ) is extensively utilized to assess adolescent psychosocial problems. Despite its global use, the instrument’s reliability and validity across diverse ethnic populations remain under-examined. This study evaluates the reliability and validity of the SDQ among adolescents from an ethnic young cohort from Northeast India. Methodology: The present study followed a cross-sectional descriptive study design. The population for the study comprised children aged 13–17 years, studying in various government and public schools located in districts in Northeast India. In this study, a total sample size of 400 participants was selected. The SDQ was used. The researcher used the Statistical Package for the Social Sciences (SPSS) version 23 to analyze and measure the data. The study was undertaken with the approval of the scientific committee and ethical committee. Results: The internal consistency of the SDQ, as indicated by a Cronbach’s α of 0.846, suggests high reliability. Exploratory factor analysis identified five distinct factors from the SDQ items, with Bartlett’s Test of Sphericity and the Kaiser–Meyer–Olkin (KMO) measure confirming the appropriateness of factor analysis (χ² =1880, df = 276, P < 0.001; KMO = 0.848). Factors were deemed significant with loadings ≥0.3. Conclusion: The findings affirm the SDQ’s reliability and factor structure within this multiethnic context of Northeast India, underscoring its potential as a valid tool for screening psychosocial issues among diverse ethnic groups. This validation enhances the SDQ’s applicability for mental health assessments and interventions across varied Indian ethnicities.