Parenteral prostacyclin is the most-effective therapy for patients with pulmonary arterial hypertension. Administration is complex, and administration errors are potentially life threatening. Hospital policies to minimize the risk to patients are necessary, but their effectiveness has not been well studied. We quantified the adverse event incident rate per at-risk patient day in a tertiary care hospital with an established parenteral prostacyclin policy. Patients on parenteral prostacyclin including new initiations from January 2003 to January 2013 were identified, encompassing 386 discrete admissions. Reports of adverse events were obtained from the inpatient risk feedback–reporting process and detailed chart review. Policy-divergent events were analyzed both categorically and by the degree of severity. Overall, 153 total policy-divergent events were identified. Data analysis indicated an incident rate of 45.9 per 1,000 patient days. In total, 21 of 153 potential errors reached the patient, translating to an incident rate of 6.3 per 1,000 patient days. Incident rate for “serious symptomatic” or “catastrophic” policy-divergent events was 3.3 per 1,000 patient days. Even with specific prostacyclin training and administration policy, there remains a small risk of adverse events in hospitalized pulmonary hypertension patients receiving parenteral prostacyclin.