Purpose@#This study was conducted to update the Nutrition Quotient for Adolescents (NQ-A), which is used to assess the overall dietary quality and foodbehavior among Korean adolescents. @*Methods@#The first 30 candidate items of the measurable eating behaviorchecklist were obtained based on a previous NQ-A checklist, the results of the seventh KoreaNational Health and Nutrition Examination Survey data, KoreaYouthRisk BehaviorSurvey data, national nutrition policies and dietary guidelines, and literature reviews. A total of 100 middle and high schoolstudents residing in Seoul and Gyeonggi Province participated in a pilot study using the 25-item checklist. Factor analysis and frequency analysis were conducted to determine if the checklist items were organized properly and whether the responses to each item were distributed adequately, respectively. As a result, 22 checklist items were selected for the nationwide survey, which was applied to 1,000 adolescent subjects with stratified sampling from 6 metropolitan cities. The construct validity of the updated NQ-A 2021 was assessed using confirmatory factor analysis. @*Results@#Twenty checklist items were determined for the final NQ-A 2021. The items were composed of three factors balance (8 items), moderation (9 items), and practice (3 items). The standardized path coefficients were used as the weights of items to determine the nutrition quotients. NQ-A 2021 and 3-factor scores were calculated according to the weights of questionnaire items. The weight for each of the 3 factors was determined as follows balance, 0.15; moderation, 0.30; and practice, 0.55. @*Conclusion@#The updated NQ-A 2021 is a useful instrument for easily and quickly evaluating the dietary qualities and eating behaviors of Korean adolescents