OBJECTIVE To investigate the prevalence and associated factors of retinal nerve fiber layer defects (RNFLDs) in a Korean population. METHODS The Korea National Health and Nutrition Examination Survey (KNHANES) is a population-based study using a complex, stratified, multistage, probability-cluster survey. We performed a review of 2008-2012 data from the KNHANES. Two masked ophthalmologists evaluated fundus photography to detect RNFLDs. All participants underwent ocular and systemic evaluations. RESULTS A total of 28,637 subjects aged ≥ 19 years with at least one evaluable fundus photograph were enrolled. The estimated prevalence of RNFLDs in this Korean population was 4.8% (95% confidence interval, 4.4%-5.3%). The estimated percentages of glaucomatous RNFLD and non-glaucomatous RNFLD subjects were 34.4% and 65.6%, respectively. In a multivariate analysis, the prevalence of RNFLDs was significantly associated with older age (P < 0.001), male gender (P = 0.047), glycosylated hemoglobin (P = 0.048), disc hemorrhage (P = 0.016), ISNT rule (P < 0.001), and vertical cup to disc ratio (P < 0.001). CONCLUSIONS The prevalence of RNFLDs in a large Korean population-based sample with a minimum age of 19 years was 4.8%. RNFLD prevalence was associated with old age, male gender, glycosylated hemoglobin, disc hemorrhage, and glaucomatous optic disc.