Objective Currently, several near-infrared spectroscopy oximetry devices are used for detecting cerebral ischemia during cardiopulmonary bypass (CPB) surgery. We investigated whether two different models of near-infrared spectroscopy oximetry devices affect the assessment of cerebral ischemia and its management during CPB. Methods From January 2017 to August 2017, 70 adult cardiovascular surgery cases were randomly assigned to 1 of 2 different near-infrared spectroscopy oximetry devices. The devices were INVOS 5100C (Medtronic, Minneapolis, MN, USA) (group I; n  = 35) and FORE-SIGHT ELITE (CAS Medical Systems, Branford, CT, USA) (group F; n  = 35). Results There were no significant differences in patient characteristics. The rSO 2 values were significantly higher for patients in group F than for patients in group I. Scalp–Cortex distance showed negative correlations with the mean rSO 2 values in group I ( P  = 0.01). Interventions for low rSO 2 during CPB for groups I and F were increase perfusion flow (13:5; P  = 0.03), blood transfusion (7:1; P  = 0.02), and both (6:1; P  = 0.04), respectively. The Scalp–Cortex distance in group I was significantly longer in patients who required intervention than in patients who did not (17.1 ± 2.5 vs 15.1 ± 1.6 mm; P  = 0.007). Conclusions It is inappropriate to use the same intervention criteria for different near-infrared spectroscopy oximetry devices. Moreover, brain atrophy influence rSO 2 values depending on device selection. It is important to note that inappropriate device selection may misguide perfusionists into performing unnecessary or excessive intervention during CPB.