Dental caries is the most common chronic disease among younger individuals. Dental caries and periodontal disease are considered to be pandemic diseases affecting all populations irrespective of gender, age or socioeconomic status. Dental caries is one of the global health issues in both industrial and developing countries. Untreated caries can cause severe pain and serious infections. Monitoring the prevalence of untreated as well as treated caries is a key to preventing and controlling oral disease. The aim of this study is to assess the prevalence of untreated caries in Chennai city. This is a retrospective, institutional based study. Datas of patients visiting the dental outpatient were collected. The study was conducted from June 2019 to March 2020. The sample size was calculated to be 2000. Excel tabulation was done and the data was transferred to SPSS software. The prevalence of untreated dental caries was assessed using the DMFT index. One way ANOVA test was done, to assess the mean difference in DMFT and mean D scores among different age groups in the study. The mean DMFT increased from 6.19 in the first age group 17 to 25 years to 11.39 in the last age group above 65 years. However, the D score of 4.52 among 17-25 years was significantly greater than the other and trend declined as age increased in our population (P<0.05). In conclusion the prevalence of untreated caries was greater in younger individuals who visited our dental institution as compared to older adults.