Background: Transitioning from pediatric care to adult-oriented care at age 18 (the age of transfer in most countries and jurisdictions) is a complex process for adolescents and young adults affected by chronic physical health and/or mental health conditions. The role of primary health care providers for this population is poorly understood. Perspectives from these providers, such as family physicians and other members of the primary care team, have not been explored in depth. Methods: A total of 18 participants (e.g., family physicians, social workers, nurses) were recruited from 6 Primary Care Networks in Calgary, Alberta, Canada. Semi-structured individual interviews were conducted, and transcribed verbatim. A qualitative description approach was used to analyze the data, and included thematic analysis. Results: Five distinct, yet overlapping, roles of primary health care providers for adolescents and young adults transitioning to adult care resulted from our analysis: (1) being the “common thread” (continuous accessible care); (2) caring for the “whole patient” (comprehensive care); (3) “knowing families” (family-partnered care); (4) “empowering” adolescents and young adults to develop “personal responsibility”(developmentally-appropriate care); and (5) “quarterbacking” care (coordination of specialist and/or community-based care). Participants identified potential benefits of these roles for adolescents and young adults transitioning to adult care, and barriers in practice (e.g., lack of time, having minimal involvement in pediatric care). Conclusions: Input from family physicians, who follow their patients across the lifespan and provide the majority of primary care in Canada, are critical for informing and refining recommended transition practices. Our findings provide insights, from PHC providers themselves, to bolster the rationale for primary care involvement during transitions from pediatric specialty and community-based care for AYAs. Solutions to overcome barriers for integrating primary care and specialty care for adolescents and young adults need to be identified, and tested, with input from key stakeholders.