Brian Doherty, a 33-year-old Dorchester native who took over Mayor-elect Marty Walsh's position at the Boston Building Trades in an acting capacity last April, was elected unanimously to the role of general agent for the union on Dec. 19 at the Venezia Restaurant in Dorchester.

A state representative who resigned his seat effective Friday, Walsh is set to be sworn in as mayor on Monday at Boston College.

"Brian Doherty is a great selection for General Agent of the Building Trades," said Walsh in a statement. "He is a bright, progressive, young talent with an innate ability to lead. He displayed integrity and passion overseeing the Building Pathways program. He will stand up for working families, and lead the organization in a collaborative style. He has earned the respect of the trades, developers and community leaders."

A 16-year member of Walsh's old union, Laborers Local 223, Doherty has volunteered on campaigns and starting in the summer of 2011 has been the project coordinator for the construction union's Building Pathways initiative, a pre-apprenticeship program aimed at providing opportunities for women and people of color.

Doherty said 75 people have gone through the program, which Walsh highlighted on the campaign trail.

Walsh stepped down as head of the Building and Construction Trades Council of the Metropolitan District in April to run for mayor.

"I'm very hopeful for Boston with Marty Walsh as mayor," Doherty told the News Service. He said, "I honestly, sincerely think he did a great job at the Building Trades, and I think he'll do the same in the City of Boston."

During the campaign, Walsh said he would reform the Boston Redevelopment Authority, which handles much of the development in the city, and proposed putting City Hall Plaza up for sale.

A son of immigrants, Doherty has a degree from Boston University and he was the program coordinator of the All Dorchester Sports League.