Objective: To compare effectiveness and safety of combination therapy (acetaminophen and ibuprofen) to monotherapy (ibuprofen, indomethacin, or acetaminophen alone) in treatment of the patent ductus arteriosus (PDA) in premature neonates. Methods: This was a retrospective cohort study of neonates admitted to a tertiary-level neonatal intensive care unit. Included neonates were born at <32 weeks gestation and received pharmacotherapy for PDA closure. Based on the primary therapy received, our cohort was divided into the following four groups: indomethacin alone, ibuprofen alone, acetaminophen alone, and ibuprofen and acetaminophen (in combination). Baseline characteristics, effectiveness, safety, neonatal mortality, and morbidities rates between these groups were compared. Results: One hundred and forty neonates were analyzed; 17 received combination therapy, and 123 neonates received monotherapy: 22 (17.9%) ibuprofen, 29 (23.6%) acetaminophen, and 72 (58.5%) indomethacin. The PDA closure rates were 41.7% for indomethacin, 41.2% for combination therapy, 37.9% for acetaminophen, and 31.8% for ibuprofen (P=0.100). Rates of adverse effects were comparable between the groups. Conclusion: The rate of ductal closure was not different between combination therapy and monotherapy. The study did not demonstrate any increased adverse effects in the combination group. Future well-designed prospective clinical trials are needed to guide clinical practice.