BACKGROUND Adolescents are children aged 10-19 years. Nutrition influences the growth and development during infancy, childhood and adolescence. Adolescent girls are at higher risk of anemia and undernutrition. This research was aimed to find the prevalence of anemia among adolescent girls in a tertiary care hospital. METHODS A descriptive cross-sectional study was done in the adolescent girls attending the pediatric outpatient department of a tertiary care centre from October 2020 to May 2021. After the ethical clearance from the institutional review committee, 380 adolescent girls were taken using a convenient sampling technique. Anthropometric measurements, social demography and blood for hemoglobin estimation were taken and documented in predesigned proforma. Data were analyzed with Statistical Package for the Social Sciences version 20. Point estimate at 95% Confidence Interval was done, and frequency and proportion were calculated. RESULTS Out of 380 adolescent girls, 230 (60.5%) at 95% Confidence Interval (55.56-65.41) were anemic with mean hemoglobin of 11.138±1.954 gm/dl. The mean age was 14.57±2.107 years. CONCLUSIONS This study showed a higher prevalence of anemia than the national data. Proper education regarding personal and menstrual hygiene, weekly supplementation of iron in school, dietary habits and uplifting of economic status can prevent anemia in this population.