Introduction: Adolescence is a critical period of rapid growth and development, during which nutritional status plays a pivotal role. The COVID-19 pandemic and the recent economic crisis in Sri Lanka may have adversely impacted the nutritional status of adolescents. Objectives: This study was conducted to assess the nutritional status and prevalence of malnutrition among adolescent schoolchildren in Galle district, Sri Lanka. Methodology: A cross sectional study was conducted among 876 adolescent schoolchildren aged 16-19 years attending schools in Galle district. Sample was selected using cluster sampling technique. Nutritional status of the adolescents was assessed using Body Mass Index (BMI) for age. Data were analyzed using Statistical Package for Social Sciences software, version 30 using descriptive statistics. Results: Mean age (SD) of the adolescents was 16.27 (0.58) years. Among the adolescents, 51.7% were females while 48.3% were males. Among the females, 70.9% had normal BMI for age, 13.5% had thinness, 5.1% had severe thinness, 9.9% had overweight and 0.7% had obesity . Among the males, 53.2% had normal BMI for age, 23.4% had thinness, 14.9% had severe thinness, 6.9% had overweight and 1.7% had obesity . Overall, malnutrition was reported among 37 .6% of the adolescents. Conclusions: A considerable proportion of adolescent schoolchildren in Galle district were affected by malnutrition, with thinness being more prevalent among males while overweight was more common among females. These findings highlight the coexistence of undernutrition and overnutrition among adolescents, emphasizing the need for targeted nutritional interventions and regular monitoring to improve adolescent nutritional health in Sri Lanka.