Objective: To identify the factors associated with unsuccessful pessary fitting and reasons for pessary discontinuation in Korean women with pelvic organ prolapse (POP). Methods: The medical records of 234 patients who underwent pessary fitting for the management of symptomatic POP were retrospectively reviewed. A ring pessary with or without support was used. Successful pessary fitting was defined as the ability to wear a pessary for 2 weeks without any discomfort. Factors associated with unsuccessful pessary fitting were determined using a multivariable logistic regression analysis. A Kaplan-Meier survival curve was obtained to examine the probability of continuing pessary use over the follow-up period. The reasons for the discontinuation of pessary were identified. Results: Two-hundred-and-twenty-five women were included in the analysis. The rate of unsuccessful pessary fitting was 40%. Prior hysterectomy (odds ratio [OR], 4.13; 95% confidence interval [CI], 1.81-9.42) and POP quantification stage III-IV (OR, 2.49; 95% CI, 1.28-4.85) were independent risk factors for unsuccessful pessary fitting. Among the patients with successful pessary fitting, the median time to discontinuation of pessary use was 4 years. The most common causes of discontinued use were vaginal erosion (45.3%) and urinary incontinence (26.5%). Conclusion Patients with a history of hysterectomy and advanced-stage POP are at risk for an unsuccessful fitting of the ring pessary. Vaginal erosion is the main reason for discontinued use among patients with successful pessary fitting.