Patients with chronic obstructive pulmonary disease (COPD) are predisposed to respiratory failure with ventilator dependency. This study aims to determine the risk of prolonged mechanical ventilation (PMV), defined as 22 days or more of mechanical ventilation dependency after the first day of hospital admission (index date) in patients diagnosed with COPD. A retrospective cohort was conducted using medical claim data of Taiwan's National Health Insurance Research Database. Eligible study subjects were those who had a diagnosis of COPD made between January 1, 2005 and December 31, 2009. Patients were then followed until being registered as a PMV case, death, or the end of the study. The comorbidities were measured from January 1, 1997 to the index date by the ICD-9 code. The study sample consisted of 6,341 patients with COPD with a mean age of 73.89 (± 12.01) years. Over a maximum of 6 years of follow-up, 654 patients developed PMV dependency, with an incidence density of 41.56 per 1,000 person-years. Patients aged 70 years and older were at significantly increased risk for PMV dependency, compared to those aged 40-49 years after adjusting for confounders. Expenses per visit and hospital visits per year, representing the severity of the COPD, were also associated with an elevated risk of PMV. Most patients developed PMV dependency within the first two years after the index date. Physicians should be aware that elderly patients with COPD have a high risk of PMV after first hospitalization, and these patients need to be closely monitored.