During perioperative care, the continuous measurement of blood pressure (BP) provides superior physiological monitoring compared to intermittent techniques, especially for patients with comorbid conditions such as severe obesity. The current study prospectively assesses the accuracy of a continuous, noninvasive BP device in severely obese adolescents and young adults. The technology evaluated was the CNAP Monitor 500, developed by CNSystems AG (Graz, Austria). The study cohort was composed of severely obese adolescents (body mass index ≥ 35 kg/m2) undergoing a surgical weight loss procedure (robotically assisted or laparoscopic vertical sleeve gastrectomy or laparoscopic Roux-en-Y gastric bypass). Systolic (sBP), diastolic (dBP), and mean arterial (MAP) blood pressure readings were captured from an intraoperatively placed radial arterial cannula (AC) and the CNAP device at regular intervals (once per minute) during anesthetic care. The study cohort consisted of 18 severely obese subjects undergoing weight loss surgery. A total of 2,159 pairs each of sBP, dBP, and MAP values obtained. The correlation coefficient between the AC and the CNAP device was 0.655, 0.667, and 0.783 for the sBP, dBP, and MAP, respectively. The CNAP values (sBP, dBP, MAP) were ≤5 mmHg from the AC values in 33, 40, and 41 % of the values, respectively. The difference was more than 10 mmHg (sBP, dBP, MAP) in 39, 28, and 25 % of the values, respectively. Using a Bland–Altman analysis, the precision and bias for the sBP, dBP, and MAP were 0.3 ± 14.2, −1.3 ± 9.5, and −0.6 ± 8.6 mmHg, respectively. When compared to previous studies in the adult population, the accuracy of the CNAP device in a cohort of severely obese adolescents undergoing weight loss surgery was slightly less than previously reported. The current data demonstrate a clinically useful trend of the CNAP device with arterial values in this challenging patient population in whom an arterial cannula may at times be difficult.