Silver Diamine Fluoride (SDF) is a clinically applied treatment that controls active dental caries and aids in preventing further progression of the caries process. Aim of study. To establish the effectiveness of SDF in arresting primary tooth caries in 6-12-year-old Cambodian children. A longitudinal observational study was conducted using a convenience sample of 167 children from Api Wat Meanchey primary school who were recruited following consent. Participants received two applications of SDF (Cariestop 30%, Biodinamica, Ibipora, Brazil) at six-month intervals and follow-up examinations after 1 year. Oral health education was provided to the participants at the beginning of the study and a school tooth brushing program was in place. 118 (70.7%) of the participants were followed up after one year of which 56.8% were female. The mean dmft/DMFT at baseline was 10.5 (SD 7.6) / 4.6 (SD 4.9). At follow up 82.5% of open carious lesions were arrested. Application of 30% SDF solution two times per year was an effective way to manage caries in this very high caries risk population.