Aims/hypothesis To examine whether childhood adversity is related to development of type 2 diabetes in early adulthood (16 to 38 years) among men and women.Methods We used nationwide register data of 1,277,429 individuals born in Denmark between 1 January 1980 and 31 December 2001, who were still resident in Denmark and without diabetes at age 16 years. Individuals were divided into five childhood adversity groups based on their yearly exposure to childhood adversities (from age 0-15 years) across three dimensions: material deprivation, loss or threat of loss, and family dynamics. We estimated HR and hazard differences (HD) for type 2 diabetes according to the childhood adversity groups using Cox proportional hazards and Aalen additive hazards models.Results During follow-up from age 16 to 31 December 2018, 4860 individuals developed type 2 diabetes. Compared with the low adversity group, the risk of type 2 diabetes was higher in all other childhood adversity groups among both men and women. For example, the risk was higher in the high adversity group characterised by high rates of adversity across all three dimensions among men (HR 2.41; 95% CI 2.04, 2.85) and women (1.58; 1.31, 1.91), translating into 36.2 (25.9, 46.5) additional cases of type 2 diabetes per 100,000 person-years among men and 18.6 (8.2, 29.0) among women.Conclusions/interpretation Individuals who experienced childhood adversity are at higher risk of developing type 2 diabetes in early adulthood. Intervening upon proximal determinants of adversity may help reduce the number of type 2 diabetes cases among young adults.