Background: Statins have been known to increase the risk of incident type 2 diabetes mellitus (DM); however, other factors, especially hypertension, are also associated with DM development. Objective: We investigated whether statin use increases the risk of DM and further analyzed whether the relation between statin use and incident DM differs according to the presence of hypertension and gender. Methods: From a nationwide health-screening cohort, 40,164 participants with total cholesterol levels ≥eve mg/dL and without pre-diagnosed DM, cardiovascular disease, or cancer, who underwent a series of regular health check-ups, were enrolled. Statin users were defined as participants who were prescribed statins more than twice during 6 months. Results: There were 17,798 statin non-users and 22,366 statin users. During 7.66±3.21 years of follow-up, incident DM developed in 5.68% of statin non-users and 7.64% of statin users. Among the entire study population, statin use was associated with new-onset DM after adjusting for clinical risk factors. In sub-analysis according to hypertension, statin use significantly increased the risk of incident DM only in normotensive patients [hazard ratio (HR) 1.31, 95% confidence interval (CI) 1.09 to 1.58, p = 0.004], and not in hypertensive patients (p>0.05). Furthermore, continuous statin use was strongly associated with new-onset DM in women, regardless of hypertension presence (all p<0.05). However, in men, statin was associated with new-onset DM only in normotensive males (HR 1.61, 95% CI 1.35 to 1.92, p<0.001) and not in hypertensive males (p>0.05). Conclusions: Statin use increased the risk of new-onset DM only in normotensive patients and hypertensive women, suggesting that these groups should be more carefully monitored for the development of DM during the course of follow-up.