Impacted mandibular third molars may predispose an individual to other problems, such as pericoronitis, orofacial infections, periodontitis, external resorption of the adjacent tooth etc. Because the carious lesion in the distal surface of the 2nd molar is difficult to detect, such teeth could develop pulpitis or apical periodontitis. The aim of the study was to assess the association between impacted mandibular third molar and distal deep caries on mandibular second molar. Dental records of patients reported to the institution between June 2019 to March 2020 were retrieved. Dental records of patients who underwent extraction of impacted mandibular third molar teeth was assessed (n=641). Age, gender, type of impaction of third molar based on winter’s classification, presence and absence of distal caries on the corresponding mandibular second molar was recorded. The frequency distribution was analyzed with descriptive statistics, the association between type of impaction and dental caries on second molar was analyzed by chi square test using SPSS. Results from this study showed that horizontal impaction (3.12%) was commonly associated with distal deep caries statistically significant (p-0.02, p<0.05). Within the limitations of the study, it was concluded that 5.93% of patients with impacted mandibular third molar had distal dental caries on the mandibular second molar. This association was more often identified in the age group of 36-65 years with relatively higher predilection in the male population. Considering the type of impaction, distal caries on the mandibular second molar was commonly seen in the cases of horizontally impacted third molars.