Radiation therapy is the main treatment methods that can be used alone and in combination with other therapeutic methods. It is obvious that without dental care, complications of radiation therapy cannot be avoided, or reduce the severity of complications. The aim of this study was to assess the knowledge rate of Ardabil Dentists regarding Dental treatments in Patients undergone Radiotherapy Procedures Methods and Materials: This cross-sectional study was performed on 120 Ardabil dentists. Data collected by a questionnaire by interview and then analyzed by SPSS.19. using statistical methods. Results: 58.3% of dentists were female and the mean age of dentists was 22.6__ampersandsignplusmn;7. The mean time from graduation was 6.1__ampersandsignplusmn;5.4 years. 51.7% of dentists had moderate knowledge. There was no significant relation between graduation, age and sex of dentists with knowledge. Conclusion: Results showed that the knowledge of dentists in Ardabil about patients undergoing radiation was in moderate level, Therefor we recommend some established educational programs in this field.