This retrospective study aimed to compare systolic and diastolic blood pressures between patients with acute kidney injury (AKI) after initiation of angiotensin-converting enzyme (ACE) inhibitor therapy and those of patients who do not experience AKI after ACE inhibitor therapy. Of 332 patients who received an ACE inhibitor as inpatients at our institution from 1 January 2010 to 1 July 2012, 20 patients had a doubling of serum creatinine (SCr) within 72 h after initiation or dose uptitration of an ACE inhibitor (AKI group). These cases were matched one to four by age and gender to patients who received an ACE inhibitor but did not have a doubling of SCr (control group). The patients in the AKI group had a significantly greater decrease in systolic and diastolic blood pressures before their AKI than the control group. Pediatric patients who experience ACE inhibitor-associated AKI have a significantly greater decrease in blood pressure than patients who do not experience ACE inhibitor-associated AKI. The authors suggest that the risk and benefits of ACE inhibitor use be stringently evaluated before initiation of therapy.