Assessing patient-reported health behaviors is a critical first step in prioritizing prevention in primary care. We assessed the feasibility of point-of-care behavioral health assessment in 9 diverse primary care practices, including 4 federally qualified health centers (FQHCs), 4 practice-based research network practices, and a Department of Veterans Affairs practice.In this prospective mixed-methods study, practices were asked to integrate a standardized paper-based health behavior and mental health assessment into their workflow for ≥50 patients. We used 3 data sources to examine the implementation process: (1) patient responses to the health assessment, (2) patient feedback surveys about how assessments were used during encounters, and (3) postimplementation interviews.Most nonurgent patients (71%) visiting the participating practices during the implementation period completed the health assessment, but reach varied by practice (range, 59% to 88%). Unhealthy diet, sedentary lifestyle, and stress were the most common patient problems, with similar frequencies observed across practices. The median number of "positive screens" per patient was similar among FQHCs (3.7 positives; standard deviation [SD], 1.8), practice-based research network practices (3.8 positives; SD, 1.9), and the Veterans Affairs clinic (4.1 positives; SD, 2.0). Primary care clinicians discussed assessment results with patients about half of the time (54%), with considerable variation between practices (range, 13% to 66%; lowest use among FQHC clinicians). Although clinicians were interested in routinely implementing assessments, many reported not feeling confident of having resources or support to address all patients' behavioral health needs.Primary care practices will need to revamp their patient-reported data collection processes to integrate routine health behavior assessments. Implementation support will be required if health assessments are to be actively used as part of routine primary care.