Purpose Type 2 diabetes requires patients to make lifestyle changes and perform daily self-care. To determine at what stages patients may need particular self-management support, we examined (1) whether patients' performance of self-care related to their diabetes duration, and (2) whether illness characteristics (treatment and complications) and diabetes-related distress influenced this relationship. Methods Cross-sectional data from 590 type 2 diabetes patients were analysed through linear and logistic regression analysis. Self-care behaviours were assessed by the revised Summary of Diabetes Self-Care Activities (SDSCA) measure. Diabetes duration (model 1), treatment and complications (model 2), and distress, as assessed by the Problem Areas In Diabetes (PAID) scale (model 3), were stepwise included. Sociodemographic characteristics were added to all models to account for confounding. Results Patients with a longer history of diabetes were less physically active, but monitored their blood glucose levels more frequently than more recently diagnosed patients. These relationships were mediated by the presence of complications and the use of insulin, with lower levels of physical activity being found among patients with macrovascular complications and higher frequencies of glucose monitoring among patients on insulin. All predictors together explained maximally 5% of the variance in self-care, except for glucose monitoring (37%) and smoking (11%). Conclusion Type 2 diabetes patients' self-care activity changes over the course of illness. To provide tailored self-management support, diabetes care providers should take into account patients' phase of illness, including their treatment and complications, as well as their personal characteristics and distress level.