To develop a patient-centred, group-based self-management programme (X-PERT), based on theories of empowerment and discovery learning, and to assess the effectiveness of the programme on clinical, lifestyle and psychosocial outcomes. Adults with Type 2 diabetes (n = 314), living in Burnley, Pendle or Rossendale, Lancashire, UK were randomized to either individual appointments (control group) (n = 157) or the X-PERT Programme (n = 157). X-PERT patients were invited to attend six 2-h group sessions of self-management education. Outcomes were assessed at baseline, 4 and 14 months. One hundred and forty-nine participants (95%) attended the X-PERT Programme, with 128 (82%) attending four or more sessions. By 14 months the X-PERT group compared with the control group showed significant improvements in the mean HbA1c (- 0.6% vs. + 0.1%, repeated measures anova, P < 0.001). The number needed to treat (NNT) for preventing diabetes medication increase was 4 [95% confidence interval (CI) 3, 7] and NNT for reducing diabetes medication was 7 (95% CI 5, 11). Statistically significant improvements were also shown in the X-PERT patients compared with the control patients for body weight, body mass index (BMI), waist circumference, total cholesterol, self-empowerment, diabetes knowledge, physical activity levels, foot care, fruit and vegetable intake, enjoyment of food and treatment satisfaction. Participation in the X-PERT Programme by adults with Type 2 diabetes was shown at 14 months to have led to improved glycaemic control, reduced total cholesterol level, body weight, BMI and waist circumference, reduced requirement for diabetes medication, increased consumption of fruit and vegetables, enjoyment of food, knowledge of diabetes, self-empowerment, self-management skills and treatment satisfaction.