Background: Valid and reliable research tools to assess children¿s and adolescent¿s health-related behaviour are highly needed across the globe. Rapid economic development, globalization, and associated lifestyle challenges observed in most countries support the need for high-quality evidence in adolescents to target health-promoting policies and interventions. This study aims to examine the test¿retest reliability of selected well-being, physical and screen-time related siting activities, and eating behaviour items of the Health Behaviour in School-Aged Children (HBSC) questionnaire in a sample of Vietnamese adolescents. Methods: Data were collected in autumn 2018 in Vietnam (3-week interval). The sample consisted of 410 adolescents (41.0% of boys; mean age = 12.61; SD = 1.24).Test¿retest reliability was evaluated using the single measure Intraclass Correlation Coefficients (ICC) and Cohen¿s kappa statistic stratified by sex, grade and place of residence (urban or rural). Results: The reliability analyses of the well-being items were poor to good ICC values (0.43¿0.79) and moderate to large Cohen¿s kappa values (0.33¿0.77). The physical activity and eating behaviour items were moderate (ICC = 0.54¿0.65; Cohen¿s kappa = 0.38¿0.57). The screen-time related siting activities items were moderate to large (ICC = 0.51¿0.72; Cohen¿s kappa = 0.42¿0.53). There was more item stability among females than males. The social media item was not as stable for 6th graders (ICC = 0.45) compared with older adolescents (ICC 0.68¿0.77). Conclusions: The findings show that with regards to age, sex and place of residence, self-reported health, life satisfaction, physical and screen-time related siting activities, as well as eating behaviour items of the HBSC questionnaire have a sufficient test¿retest reliability to be used in national self-report surveys for Vietnamese adolescents while health complaints items showed borderline reliability.