Abstract Purpose Previous studies have demonstrated lower prostate-specific antigen (PSA) concentrations in men with type 2 diabetes (T2DM), paralleling the reported lower prevalence of prostate cancer among diabetic men. Data on PSA in men with type 1 diabetes (T1DM), in whom insulin and obesity profiles differ from those in T2DM, are lacking. The objective of this study was to examine the relationship between long-term glycemic control and PSA in men with T1DM. Materials & Methods Total PSA was measured at one time in 639 men in the Epidemiology of Diabetes Interventions and Complications (EDIC) study, the observational follow up of participants in the Diabetes Control and Complications Trial (DCCT). The relationship between DCCT/EDIC weighted mean HbA1c and log PSA was assessed using linear regression modeling after adjusting for age, body mass index (BMI), total testosterone, statin and thiazide medication use, diabetes duration, and DCCT randomization arm and cohort. Results The subjects had a median age of 52 years, BMI of 28.4 kg/m2 and DCCT/EDIC time weighted HbA1c of 7.9%. Total median (interquartile range) for PSA levels was 0.64 (0.43, 1.05). PSA levels increased significantly with age (p<0.0001) and with lower time weighted HbA1c (p<0.0001). Each 10% increase in HbA1c was accompanied by an 11% reduction in PSA (p=0.0001). Conclusions PSA levels decrease as HbA1c increases in men with T1DM. This relationship is independent of age, BMI, androgen levels, medication use and measures of diabetes severity, which suggest that factors related to glycemia may be directly affecting PSA levels.