INTRODUCTION: The US Preventive Services Task Force recommends out-of-office blood pressure (BP) measurement before making a new hypertension diagnosis and initiating treatment, using 24-hour ambulatory (ABPM) or home BP monitoring. However, this approach is not common. METHODS: e-mail-linked surveys were sent to primary care team members (n = 421) from 10 clinics. The sample included medical assistants, licensed practical nurses, registered nurses, and advanced practice registered nurses (LPN/RN/APRNs), physician assistants (PAs), and physicians. Those licensed to diagnosis hypertension (physician/PA/APRNs) received additional questions. Data were collected from November 2017 to July 2019. RESULTS: 2-thirds of invitees responded (163 MA/LPN/RNs, 86 physicians, and 33 PA/APRNs). When making a new hypertension diagnosis, most respondents believed that BP measured manually with a stethoscope (78.6%) or ABPM (84.2%) were very or highly accurate. In contrast, most did not believe that automated clinic BPs, home BP, or kiosk BP measurements were very or highly accurate. Almost all reported always or almost always relying on clinic BP measurements in making a diagnosis (95.7%), but most physician/PA/APRNs (60.5%) would prefer ABPM if it was readily available. Very few physician/PA/APRNs used the guideline-concordant diagnostic threshold (135/85 mmHg) with home monitoring (14.0%) or ABPM (8.4%), with 140/90 mmHg the most commonly reported threshold for home (59.4%) and ABPM (49.6%). DISCUSSION: Our study found health care professional knowledge, beliefs, and practices gaps in diagnosing hypertension. These gaps could lead to clinical care that is not aligned with guidelines. CONCLUSION: System changes and interventions to increase use of evidence-based practices could improve hypertension diagnosis and outcomes.