The purpose of this study was to test whether elevated glycated hemoglobin A1c (HbA1c) levels are associated with cancer incidence in the Korean population. In cohorts of the Korea Genome and Epidemiology Study (KoGES) consortium, we tested whether plasma levels of HbA1c were associated with all-site cancer incidence in 7,822 participants without any known history of cancer or diabetes. Cancer developed in 117 participants during the follow-up period. Subjects were subdivided into 3 categories according observed levels of HbA1c (< 5.7%, low; ≥ 5.7% and < 6.5%, mid; and ≥ 6.5%, high). The adjusted hazard ratio for all-site cancer was 3.03 (95% confidence intervals, 1.54–5.96) for the high HbA1c group relative to the low HbA1c group after adjusting for covariates. Higher circulating HbA1c levels were associated with an increased risk of all-site cancer in Korean population.