Suffolk County Sheriff Steve Tompkins on Tuesday endorsed Michelle Wu for mayor, citing her “tireless advocacy” for addiction recovery treatment and mental health services.

“I have known Michelle for nearly a decade, and over that span, I have seen firsthand the pure devotion to service that she has for the City of Boston and the people and organizations that operate within its borders,” Tompkins said in a statement.

Tompkins was appointed sheriff by Gov. Deval Patrick in 2013. He won his first term in November 2014. He also chairs the Roxbury Community College board of trustees.

Wu, a councillor at-large since 2014, has worked for the late Mayor Thomas Menino and US Sen. Elizabeth Warren.

The endorsement was announced outside the Reggie Lewis Center in Roxbury.

“Sheriff Tompkins has worked for years to provide educational opportunities, economic development and reentry support for formerly incarcerated community members,” she said in her own statement. “I look forward to partnering with him in City Hall to ensure all our neighborhoods have the resources they need to be safe, supported and healthy.”

Wu is one of five major mayoral candidates on the Sept. 14 ballot. The others are Acting Mayor Kim Janey, City Councillors Andrea Campbell and Annissa Essaibi George, and former city economic development chief John Barros.

The previous Suffolk County sheriff, Andrea Cabral, has endorsed Campbell, the councillor for District 4 (Dorchester and Mattapan).