Background and objective Long-term effectiveness of action plans in patients with chronic obstructive pulmonary disease (COPD) is minimally investigated. We have evaluated the (cost-)effectiveness of a self-management programme with or without self-treatment of exacerbations after 2 years follow-up. Methods Self-management with or without self-treatment of exacerbations was randomly assigned to patients. All patients participated in four self-management meetings. Patients in the self-treatment group (STG) also learned to use an action plan to start a course of prednisolone and/or antibiotics in case of worsening of symptoms. Primary outcome was the duration and severity of exacerbations. Results Data of 70 COPD patients in the STG and 72 patients in the control group (CG) were analysed. Over 2 years, the median number of exacerbation days was significantly lower in the STG (50, IQR: 32–115) compared with the CG (82, IQR: 22–186) (P = 0.047), as was the mean symptom score of an exacerbation (STG: 43.4, IQR 27.2–68.6 vs CG: 55.9, IQR: 31.2–96.8) (P = 0.029). Also, patients in the STG visited the respiratory physician and emergency department less frequently than patients in the CG with incidence rate ratios of 1.52 (95% CI: 1.28–1.79) and 2.27 (95% CI: 1.11–4.62), respectively. Direct medical costs per patient over 2 years were €1078 lower in the STG. Conclusion Self-treatment of exacerbations is beneficial in COPD patients without significant comorbidities because it reduces exacerbation duration, exacerbation severity and health-care utilization leading to considerable cost savings.