BACKGROUND: Adolescent population Global Diet Quality Score (GDQS) is uncommon in low-income settings. Though Global Diet Quality Score is a good measure of dietary diversity, it has not been used in assessing nutritional outcomes among adolescents. Therefore, the aim of this study is to assess school-attending adolescents stunting and thinness status and associations with global diet quality scores in Addis Ababa. METHODS: A school-based cross-sectional study was conducted among school-attending adolescents in the age group of 10-14 years in urban settings in Ethiopia. A multi-stage stratified random sampling procedure was used to select schools and students. A total of 1200 adolescents were included in the study. Binary and Multinomial logistic regression analyses were used to determine the predictors of stunting and thinness respectively. RESULTS: The proportion of school-attending adolescents stunting was 8.17% (95% CI: 6.74%,9.85%) and their thinness status 12.66% (95% CI: 10.89%, 14.67%). The overall mean GDQS food groups for Seven days period consumed were 19.99 + 2.81 SD. Male adolescents were 1.95 times more likely to be stunted compared to female adolescents (1.95; 95%CI: 1.11,3.39). Frequent consumption of low-fat dairy increased the risk of thinness, while frequent consumption of citrus fruits and white root tubers decreased the risk of school-attending adolescents' thinness. CONCLUSION: The proportion of thin or stunted adolescents attending school was high still, about 1 in 10. Stunting and thinness have no association with the overall GDQS. Nutritional interventions need to consider frequent consumption of citrus fruits, low-fat dairy, and white roots and tubers in school adolescents' nutritional programs. Further studies should validate the GDQS for stunting and thinness of school adolescents.