Background: Health literacy is the capacity of individuals to obtain, understand, and interpret basic health information that is necessary to make appropriate health-related decisions. Objectives: This study aimed to investigate the association between oral health literacy and the decayed, missing, and filled teeth (DMFT) index, which was conducted in Mashhad dental clinics in 2016. Methods: In this cross-sectional study, 380 patients referred to private and public clinics in Mashhad filled out the oral health literacy adult's questionnaire (OHL-AQ). The questionnaire contained 4 sections: reading, numeracy, listening, and decision making. Each correct answer was assigned a score of 1 and incorrect or no response were assigned with zero score. The DMFT index was evaluated based on decayed, missing, and filling teeth. Data analysis was performed using chi-square and linear regression tests. Results: The mean score for oral health literacy was 10.6 ± 3.4. Among patients 46.8% had favorable oral health literacy level, 19.7% were with relatively favorable, and 33.4% were with unfavorable health literacy levels. The average of the DMFT index in the studied group was 8.3 ± 4.9 and was higher among males than females. A significant correlation between the health literacy level and the DMFT index was observed; however, the correlation was negative and weak (R=-0.127). Conclusions: The average of oral health literacy level for the entire study population was relatively appropriate, and the majority of the subjects (46.8%) represented a good oral health literacy level. Furthermore, education, economic status, and collecting information from different sources of oral health are important factors affecting the level of oral health literacy.