Introduction: The study of endodontic epidemiology may help in prediction of future needs for dental treatment in a dentate population. The prevalence of endodontically treated teeth in the Malaysian population has never been investigated and their estimates have been based on studies from other countries. This study evaluated the prevalence of endodontically treated teeth in an adult Malaysian population attending a dental school clinic in northern Malaysia. Methods: The sample of this cross-sectional study examined the orthopantograms of 1663 patients in age group 18 to 75 years old, visiting the clinics of AIMST dental institute. A total of 33462 teeth were examined by four calibrated professionals. Any radiographic evidence of presence of radio-opaque material in pulp space was considered as endodontic treatment for the particular tooth. Third molars, supernumerary teeth and faulty radiographs were excluded from the study. Data was recorded with respect to gender, age and ethnicity of the patient and also the type of tooth. It was statistically analysed using Odds ratio, logistic regression and chi-square test. Results: There was a greater prevalence of endodontic treatment in females than males and 31 to 40 years age group. Malay population had higher number of cases of overall endodontically treated teeth, while Indian population showed highest percentage of cases within any ethnic group. Maxillary molars and mandibular molars were most frequently treated teeth, whereas canines showed the lowest prevalence. Findings were more significantly higher for maxillary teeth than mandibular teeth and for left side than right side. Conclusion: The prevalence of endodontically treated teeth in the Malaysian adult population was higher than that observed in epidemiological studies from other countries. This might is considered due to the higher incidence of caries and awareness emerging among the sub-population for preserving natural teeth. The results also concluded the necessity of more educational programs in Endodontics.