© 2022 Elsevier Inc.Purpose: The purpose of this study is to evaluate the relationship between adolescents' nutritional attitudes, obesity awareness, and diet quality with their self-reported anthropometric measurements taken during the COVID-19 pandemic. Design and methods: This cross-sectional type of study was conducted in a district in the south of Turkey. The research was carried out online with 907 adolescents who agreed to participate voluntarily. Results: Among the adolescents, 28.5% considered themselves overweight, and 32.1% were currently trying to lose weight. According to BMI, 16.1% were affected by overweight/obesity. Adolescents' nutritional attitudes and obesity awareness levels were moderate, while their KIDMED nutritional habits were also moderate. In this study, a negative relationship was found between the adolescents' ASHN mean scores and their body weight, waist circumference, hip circumference, neck circumference, waist/hip ratio and waist/height ratio measurements; and between their OAS mean scores and their body weight, waist circumference, waist/hip ratio and waist/height ratio measurements; and between their KIDMED index scores and their waist/height ratio measurements (p < 0.001). Conclusions: The rate of adolescents who perceive themselves as overweight is higher than the results obtained from the measurement values. BMI levels and other anthropometric measurement values of adolescents with positive nutrition attitudes and physical activity behaviours are also positively affected. Practice implications: This study may have a significant impact on the formulation and implementation of interventions to prevent obesity and increase physical activity for school health nurses. Since the pandemic is still continuing, healthcare providers must stress the risk of obesity in adolescence.