Motivational interviews used for health behavioural change requires several sessions and expert consultations. A practical method is needed to promote oral hygiene habits. The aim of the study was to develop a video as a new motivational intervention method combining several health behaviour change theories to improve flossing behaviour. A questionnaire about individual psychosocial characteristics was conducted to 30 volunteer dental patients. Plaque index (PI) scores were calculated and a video about flossing was shown the patients. The second PI measurements were performed after 2months. The video including flossing instructions and expressions of performers acting dental patients was produced to test as a motivational method. Cues used in the video were generated according to health behaviour change theories and models under the supervision of an expert team. Content validity ratio (CVR) and content validity index (I-CVI) of the video and reliability of the questionnaire was determined. First and second PI scores were compared to assess the effect of the video. Correlation between answers of the questionnaire and PI changes were tested. The average I-CVIs of the video was 0.93, CVR of video items was 1, I-CVIs of 5 items was 80% and of 10 was 100%. Cronbach's alpha of the questionnaire was 0.93. PI scores significantly decreased after 2months (p<0.001). A single session motivational intervention via a video based on health psychological models and theories was efficacious in improving oral hygiene and flossing behaviour in the short term.