We have evaluated the impact of a school-based intervention on oral health knowledge, behaviours, and oral health status of adolescents in vietnam. This 6-month study included 462 adolescents aged 12 years from four selected schools in hue city, vietnam. The intervention group received a 15-min lecture by a dentist and hands-on session on mouth observation and toothbrush-ing skills. The control group did not engage in any educational activities during the follow-up pe-riod. Data were collected at baseline and 6 months through a survey questionnaire and clinical ex-amination. The debris index was used for dental plaque; the papillary, marginal, attached gingiva index for gingivitis; and the decayed, missing, and filled teeth index (world health organization modification) for dental caries. Difference-in-difference analysis was used to compare changes between the groups. After 6 months, the control tended to show decreased toothbrushing frequency and increased dental plaque accumulation. The participants in the intervention group showed improved oral health knowledge (p <0.01), Behavior (p < 0.05), And hygiene (p < 0.001) Compared to the control group. However, the intervention did not improve dental caries and gingivitis. A single school-based oral health education program can help adolescents improve oral health knowledge and prevent the deterioration of short-term oral health behavior and hygiene. 2021 By the authors. Licensee mdpi, basel, switzerland.