Aim: To analyze the effect of the brief motivational interviewing counselling approach on the knowledge, attitudes and tooth brushing practice of adolescents. Method: This research is a quasi-experiment with a pre-test and post-test design with a control group design. The research sample was 80 adolescents aged 12 and 13 years. Respondents were divided into two groups, namely 40 intervention and control groups based on inclusion criteria. The intervention group was given the MI approach, and the control group was assigned conventional dental health education. The MI group also received follow-up over the phone. Both groups filled out knowledge and attitude questionnaires before being given treatment. Plaque index and tooth brushing practice examinations were performed at baseline and four weeks after intervention. Results: The results showed an increase in the average score of oral health knowledge, attitude, tooth brushing practice in all groups. The plaque index showed a decrease in the average score in all groups. The test of both groups showed that brief MI counseling was more effective than conventional dental health education, oral health knowledge(p=<0.001), attitude((p=<0.001), tooth brushing practice( p = 0.001), plaque index (p = 0.011). Follow-up MI by telephone in adolescents is beneficial in the research during the covid-19 pandemic as a promotive and preventive effort to improve dental health behaviour. The MI method by telephone is very interesting for adolescents, easily accessible and time-efficient. Conclusion : The MI counselling brief intervention can change dental and oral health behaviour through increasing knowledge, attitudes, tooth brushing practices and reducing the dental and oral hygiene index scores of adolescents. MI interventions need to be combined with other interventions to get more effective results for research sustainability. Keywords: Motivational Interviewing, Oral Hygiene Behaviour, Adolescent