Purpose The aim of this study was to appraise the effect of community-acquired pneumonia (CAP) on inhospital mortality in critically ill acute exacerbation of COPD (AECOPD) patients admitted to a respiratory intensive care unit. Patients and methods A retrospective observational study was performed. Consecutive critically ill AECOPD patients receiving treatment in a respiratory intensive care unit were reviewed from September 1, 2012, to August 31, 2015. Categorical variables were analyzed using chi-square tests, and continuous variables were analyzed by Mann–Whitney U-test. Kaplan–Meier analysis was used to assess the association of CAP with survival of critically ill AECOPD patients for univariate analysis. Cox’s proportional hazards regression model was performed to identify risk factors for multivariate analysis. Results A total of 80 consecutive eligible individuals were reviewed. These included 38 patients with CAP and 42 patients without CAP. Patients with CAP had a higher inhospital rate of mortality than patients without CAP (42% vs 33.3%, P<0.05). Kaplan–Meier survival analysis showed that patients with CAP had a worse survival rate than patients without CAP (P<0.05). Clinical characteristics, including Acute Physiology and Chronic Health Evaluation II (APACHE II) score, C-reactive protein, and CAP, were found to be closely associated with survival of AECOPD individuals. Further multivariate Cox regression analysis confirmed that CAP and APACHE II were independent risk factors for inhospital mortality in critically ill AECOPD patients (CAP: hazard ratio, 5.29; 95% CI, 1.50–18.47, P<0.01 and APACHE II: hazard ratio, 1.20; 95% CI, 1.06–1.37, P<0.01). Conclusion CAP may be an independent risk factor for higher inhospital mortality in critically ill AECOPD patients.