Type 2 diabetes (T2D) shares some common risk factors with psoriasis. We evaluated the association between psoriasis and the risk of incident T2D among women and men in the United States in a mixed retrospective-prospective cohort study. A total of 184,395 participants were included from an older cohort of women (the Nurses' Health Study (NHS); 1996-2008), a younger cohort of women (NHS II; 1991-2007), and an older cohort of men (Health Professionals' Follow-Up Study (HPFS); 1986-2006). During 2,700,958 person-years of follow-up, 9,938 incident T2D cases were confirmed. We found a significantly increased risk of T2D associated with psoriasis only among younger women (NHS II; multivariate-adjusted relative risk (RR)=1.25, 95% confidence interval (CI): 1.05-1.49). When only including those younger than 60 years during follow-up (NHS and HPFS), we observed a nonsignificant trend toward increased risk for T2D. In a pooled analysis of the three cohorts, psoriatics younger than 60 years were at a higher risk of T2D (RR 1.26, 95% CI: 1.08-1.48 for women and RR 1.26, 95% CI: 1.08-1.46 for both sexes combined). In addition, the risk of T2D was much higher for those developing psoriasis at an early age. In conclusion, we found an association between psoriasis and the risk of T2D among individuals younger than 60 years.