Oscillatory blood pressure (OBP) with a slow cuff-deflation system has been proposed as noninvasive measurement of mean arterial pressure (MAP) in patients with continuous-flow left ventricular assist devices (LVADs). However, the challenge is that the measurement is not obtainable in certain patients. We hypothesized that the combined use of color Doppler imaging during OBP measurement (CDBP) could derive MAP accurately. We conducted a prospective observational study in critically ill patients (30 patients with continuous-flow LVADs and 30 control patients without LVADs). Triplicate OBP and CDBP measurements were performed and invasive blood pressure (IBP) was recorded. The overall success rate of OBP was 63.3% in the LVAD group and 98.9% in the control group. The CDBP was successfully obtained in 100% of all study patients. The CDBP in the LVAD group was closest to the MAP of measured IBP, while that in the control group was closest to the systolic IBP. The mean absolute differences in OBP and CDBP from the closest IBP were similar in both the control and LVAD groups. In nonpulsatile LVAD patients with a pulse pressure IBP < 10 mmHg, the success rate of OBP measurement was only 10.0%, and CDBP showed significantly reduced error in MAP measurement (mean absolute difference: OBP 23.2 ± 8.7 vs CDBP 5.2 ± 3.6 mmHg, p < 0.001). The validity of OBP measurement with a slow cuff-deflation system limited particularly in nonpulsatile LVAD patients. The concurrent use of color Doppler imaging is encouraged for more accurate measurement of MAP in patients with continuous-flow LVADs.