Ryan Monaghan
Assistant Sheriff of Support Services

Assistant Sheriff Ryan Monaghan brings more than three decades of diverse public safety experience to the San Mateo County Sheriff’s Office. Returning to a role he previously held, he continues his long-standing commitment to serving San Mateo County with humility, integrity, professionalism and collaboration.

Assistant Sheriff Monaghan most recently served as the Chief Inspector – Director of Interjurisdictional Operations for the San Mateo County District Attorney’s Office, where he led countywide, multi-agency efforts to combat human trafficking and strengthen victim-centered investigative practices. In this role, he built effective partnerships across government and nonprofit sectors to enhance the county’s coordinated response to human trafficking.

Before his work with the District Attorney’s Office, he served as assistant sheriff overseeing the Operations Division, leading major initiatives and countywide public safety operations at the Sheriff’s Office. Throughout his career, he has focused on developing policing and operational initiatives that improve service delivery, strengthen community trust and enhance public safety.

Assistant Sheriff Monaghan has more than 31 years of experience in policing, including service as Chief of Police for the Town of Tiburon and as a longtime member of the San Mateo Police Department. Assistant Sheriff Monaghan worked in and led multiple specialized duties and assignments during the formative years of his career. His career has also been shaped by his service as an adjunct associate professor at the College of San Mateo, where he taught in the Administration of Justice Department. He enjoyed igniting students’ interest in the criminal justice field and preparing the next generation of public safety professionals.

He holds a Master of Arts degree in Security Studies from the Naval Postgraduate School’s Center for Homeland Defense and Security and a Bachelor of Science degree in Criminal Justice Management.

A lifelong San Mateo County resident, Assistant Sheriff Monaghan considers it a privilege to work alongside the dedicated men and women of the Sheriff’s Office and to serve the diverse communities that make San Mateo County such a remarkable place. He remains committed to creating positive, respectful and collaborative workplace environments where employees feel valued, supported and empowered to grow.