Background: Adolescence, marked by fast growth and development in human beings, requires additional nutrients and energy to support this growth. Paying particular attention to the nutrition of adolescents, particularly girls presents a distinct chance to disrupt the ongoing cycles of malnutrition across generations. Materials and methods: A cross-sectional quantitative study was conducted within a school setting involving 271 adolescent girl’s selected using multistage sampling technique. Data was collected through a pretested questionnaire. Anthropometric measurements were used to calculate Z-scores, and analysis was conducted using WHO AnthroPlus software. Statistical analysis was performed using SPSS Version 22, and the strength of associations was determined using odds ratios (OR) along with a 95% confidence interval (CI). Variables with a p-value below 0.05 were considered statistically significant. Results: The study revealed that the prevalence of thinness was 22.9% (95% CI: 18.1–28.0%). Of which, overweight and obese subjects comprised 7.4% and 2.6% of the participants, respectively. Early adolescents' age (AOR = 2.99, 95% CI: 1.36–6.58), family size (AOR = 2.36, 95% CI: 1.23–4.52), and income (AOR = 2.71, 95% CI: 1.06–6.93) were the independent predictors of thinness among adolescent girls. Conclusion: In order to enhance the current nutritional challenges faced by adolescents, policies should take into consideration the above-mentioned determinants and work towards addressing them.