Evidence on the association between serum 25-hydroxyvitamin D (25(OH)D) concentration and all-cause and cause-specific mortality in Asians, especially Koreans, is limited. We hypothesized that high concentrations of 25(OH)D are associated with lower all-cause and cause-specific mortality in the general Korean population. This study included 27,846 adults participating in the Fourth and Fifth Korean National Health and Nutrition Examination Survey 2008-2012, followed up through December 31, 2019. Hazard ratios (HR) and 95% confidence intervals (CIs) for mortality from all causes, cardiovascular disease (CVD), and cancer were estimated using multivariable-adjusted Cox proportional hazards regression. The weighted mean serum 25(OH)D of study participants was 17.77 ng/mL; 66.5% had vitamin D deficiency (<20 ng/mL) and 94.2% had insufficient vitamin D (<30 ng/mL). During a median follow-up of 9.4 years (interquartile range, 8.1-10.6 years), 1680 deaths were documented, including 362 CVD deaths and 570 cancer deaths. Serum 25(OH)D levels ≥30 ng/mL were inversely associated with all-cause mortality (HR, 0.57; 95% CI, 0.43-0.75) compared with serum 25(OH)D levels <10 ng/mL. Based on the quartile cutoffs of serum 25(OH)D concentration, the highest quartile of serum 25(OH)D concentration (≥21.8 ng/mL) was associated with the lowest all-cause mortality (HR, 0.72; 95% CI, 0.60-0.85; P trend < .001), and CVD mortality (HR, 0.60; 95% CI, 0.42-0.85; P trend = .006). No association with cancer mortality outcome was found. In conclusion, higher serum 25(OH)D levels were associated with lower all-cause mortality in the general Korean population. An additional association was found between higher quartile of serum 25(OH)D and lower CVD mortality.