Background: According to National Oral Health Survey reports and research, Early Childhood Caries has been identified as a serious public health problem in Sri Lanka. More than 65% of preschool-aged children have dental decay and only 2% of them have had treatment. With proper interventions and commitment from public health personnel and responsible community leaders this should be a largely preventable disease. Methods: An intervention study was conducted among preschool teachers in the District of Colombo, Sri Lanka, to assess their influence on oral health promotion in the school environment. All the available 52 preschools and all 72 teachers registered under a local government authority were involved in the study. Preschools were divided into intervention group and control group based on geographically defined areas. The intervention included training preschool teachers using a manual covering health education, health promotion, incorporation of oral-health-friendly activities into the preschool curriculum, and hands-on experience of oral examination. Pre- and post- assessments were conducted with a 6 month interval. Results: After 6 months, the median oral health knowledge score of the intervention group improved from 55 to 72 (p=0.005) and the mean score for oral health related practices from 32 to 35 (p=0.032). The variables: oral-health-friendly preschool environment (p=0.02), availability of brushing facilities (p=0.005) and availability of information, education and communication materials related to oral health (p=0.004) were significantly different between the two groups after 6 months. Conclusion: Oral health promotion activities can be effectively instilled in a pre-school environment by the education of teachers. Key words: oral health, health promotion, settings approach, children, preschool, Sri Lanka