Type 2 diabetes prevalence is rising globally, and varies by socio-economic position. Amongst other factors, rising prevalence may reflect increasing incidence. Worldwide, few studies have examined population-level longitudinal trends in incident type 2 diabetes, and reports on secular trends in diabetes incidence by socio-economic measures such as educational attainment are lacking. Finland has a long-standing, comprehensive disease surveillance infrastructure. Using data collected over four decades from serial FINRISK surveys, the National Drug Reimbursement Register and the National Causes of Death Register, we examined secular trends in type 2 diabetes incidence in Finland from the 1970s to 2007. The diabetes status of 38,689 FINRISK participants aged 30–59 years at baseline assessment and without diagnosed diabetes at the time was followed for 10 years. Among men, incidence of diagnosed, pharmacologically managed type 2 diabetes increased over time. Compared with men surveyed in the 1970s, diabetes incidence was higher among men in the 1980s (adjusted HR 1.44, 95 % CI 1.13–1.84) and 1990s (adjusted HR 1.72, 1.32–2.24). Body mass index explained some, but not all of this variation. Increases occurred predominantly among men with low (adjusted HR 1980s: 2.07, 95 % CI 1.28–3.35; adjusted HR 1990s: 2.12, 95 % CI 1.28–3.53) and middle (adjusted HR 1980s: 1.30, 95 % CI 0.85–1.99; adjusted HR 1990s: 1.65, 95 % CI 1.05–2.60) educational attainment. No secular changes were apparent among women. This rising diabetes incidence among men over recent decades has occurred despite Finland’s sustained health promotion efforts. Renewed public health campaigns are urgently required. In addition to population-level initiatives, lower educational strata should be specifically targeted.