Background: Type 2 diabetes diagnosed during youth and early adulthood is aggressive and associated with a high burden of vascular complications. The increase in complications is often attributed to long disease duration and poor metabolic control. Whether people with young-onset type 2 diabetes are inherently more susceptible to long-term complications than those diagnosed in later adulthood is unclear. Methods: Prospective data from 3322 individuals, diagnosed between the age of 15 and 70 years and collected 10–25 years after diabetes diagnosis, were analysed. The cross-sectional associations between age at diagnosis and microvascular and macrovascular complications were analysed using logistic regression models, adjusted for duration of diabetes exposure and metabolic risk factors including blood pressure, cholesterol and updated mean HbA1c. Results: The prevalence of retinopathy was highest in those with young-onset type 2 diabetes (diagnosed at age 15 to <40 years). After 10–15 years' diabetes duration, the adjusted odds ratio for retinopathy in this population was 2.8 (95% CI 1.9–4.1; reference group those diagnosed at 60 to <70 years of age). The odds of retinopathy remained higher in people with young-onset type 2 diabetes after longer durations of diabetes exposure; the odds decreased with increasing age at diagnosis. This pattern was not observed in models of other complications: after 10–15 years' diabetes exposure, the adjusted odds ratios for albuminuria, peripheral neuropathy and macrovascular disease in people with young-onset type 2 diabetes were 0.5 (95% CI 0.4–0.8), 0.7 (95% CI 0.5–1.1) and 0.2 (95% CI 0.1–0.3), respectively. Conclusion: After accounting for disease duration and other important confounders, people with type 2 diabetes diagnosed in youth and early adulthood (or with a younger current age) appeared to be inherently more susceptible to retinopathy. For other complications, adjusted risk appears highest in the oldest age of diagnosis group. These data have screening and treatment target implications.