Background and Objective Twenty per cent of chronic obstructive pulmonary disease (COPD) patients are readmitted for acute exacerbation (AECOPD) within 30 days of discharge. The prognostic significance of early readmission is not fully understood. The objective of our study was to estimate the mortality risk associated with readmission for acute exacerbation within 30 days of discharge in COPD patients. Methods The cohort (n = 378) was divided into patients readmitted (n = 68) and not readmitted (n = 310) within 30 days of discharge. Clinical, laboratory, microbiological, and severity data were evaluated at admission and during hospital stay, and mortality data were recorded at four time points during follow-up: 30 days, 6 months, 1 year and 3 years. Results Patients readmitted within 30 days had poorer lung function, worse dyspnea perception and higher clinical severity. Two or more prior AECOPD (HR, 2.47; 95% CI, 1.51-4.05) was the only variable independently associated with 30-day readmission. The mortality risk during the follow-up period showed a progressive increase in patients readmitted within 30 days in comparison to patients not readmitted; moreover, 30-day readmission was an independent risk factor for mortality at 1 year (HR, 2.48; 95% CI, 1.10-5.59). In patients readmitted within 30 days, the estimated absolute increase in the mortality risk was 4% at 30 days (number needed to harm NNH, 25), 17% at 6-months (NNH, 6), 19% at 1-year (NNH, 6) and 24% at 3 years (NNH, 5). Conclusion In conclusion a readmission for AECOPD within 30 days is associated with a progressive increased long-term risk of death.