OBJECTIVES: This study investigated the risk of developing and dying from all types of cancer, as well as cancer-specific mortality, in women diagnosed with prediabetes and diabetes. METHODS: We included women aged ≥40 years who underwent cancer screening from 2009 to 2014 with follow-up until 2020. Diabetes status was determined based on fasting plasma glucose levels, self-reported history of diabetes, and the use of antidiabetic medication. We quantified the risk of cancer and mortality in the prediabetes and diabetes groups, relative to the normoglycemia group, by calculating adjusted hazard ratios (aHRs). RESULTS: The study included 8,309,393 participants with a mean age of 52.7±9.7 years. Among these participants, 522,894 cases of cancer and 193,283 deaths were detected. An increased risk of cancer was observed in both the prediabetes group (aHR, 1.03; 95% confidence interval [CI], 1.02 to 1.04) and the diabetes group (aHR, 1.13; 95% CI, 1.12 to 1.14). The highest risk was identified in those with diabetes who developed liver (aHR, 1.72; 95% CI, 1.66 to 1.79), pancreatic (aHR, 1.68; 95% CI, 1.60 to 1.76), and gallbladder cancer (aHR, 1.43; 95% CI, 1.36 to 1.51). Women with prediabetes and diabetes exhibited a 1.07-fold (95% CI, 1.05 to 1.08) and 1.38-fold (95% CI, 1.36 to 1.41) increased risk of death from cancer, respectively. CONCLUSIONS Both prediabetes and diabetes were associated with an elevated risk of cancer, as well as an increased risk of death from cancer, in middle-aged Korean women. However, the degree of risk varied depending on the specific site of the cancer.