To investigate the association between pelvic inflammatory disease (PID) and endometrial cancer (EC).We conducted a nationwide population-based retrospective cohort study, and data were obtained from the National Health Insurance Research Database. We defined 41,065 patients with PID as the PID cohort and 82,130 randomly selected patients as the control cohort through frequency matching by age and index year. PID and EC were diagnosed in accordance with the International Classification of Diseases, Ninth Revision, and Clinical Modification. Cox proportional hazards regression and Kaplan-Meier method were used in the analysis.Incidence rates of 16.1 and 9.6 per 100,000 person-years and mean follow-up durations of 4.84 and 6.63 years were observed in the PID and non-PID cohorts, respectively. After adjusting for potential risk factors, the PID cohort had a 1.79-fold higher risk of developing EC than the non-PID cohort. The incidence of EC increased with age, particularly for those aged >50 years (HR=2.45, 95% CI=1.29-4.65). Higher EC risk was also observed in the PID cohort with hypertension than in the non-PID cohort.The results of this large-scale population-based study showed an increased risk of EC in PID patients, particularly in older patients or those with hypertension. Future large-scale clinical trials are warranted to clarify the function of medication in PID-related EC progression.