BACKGROUND Ibuprofen (IBU) has been used recently for the treatment of patent ductus arteriosus (PDA) in Japan. We aimed to investigate the efficacy and adverse events of IBU and compare them with those of indomethacin (IND) as PDA treatment for extremely low-birthweight infants (ELBWIs), focusing on short-term renal function. METHODS A case-control study was conducted on 16 ELBWIs. The data from eligible patients were divided into two groups. Ten patients had undergone IND treatment (IND group) between January 2017 and June 2018, whereas six had undergone IBU treatment (IBU group) for PDA between July 2018 and December 2018. The IND group received 0.1 mg/kg/12h IND IV infusion for three doses, whereas the IBU group received 10 mg/kg IV IBU infusion followed by 5 mg/kg/day for 2 days. We compared the efficacy for PDA closure and renal impairment between the two groups. RESULTS No significant differences in primary closure rates and the PDA ligation required were observed between the two groups. No significant differences were observed between the incidence of intraventricular hemorrhage and gastrointestinal complications in both groups. Changes in urine volume (%) in the IBU group were significantly higher than in the IND group at 24-36 h post-administration. The urinary L-type fatty acid binding protein concentration level at 7 days of life was significantly lower in the IBU group than in the IND group. CONCLUSIONS Although IBU was comparable to IND in PDA closure rate, IBU was superior to short-term renal injury in ELBWIs.