Boston developer The Community Builders Inc. (TCB) has appointed Bart Mitchell as its new president and CEO, effective Jan. 1.

Mitchell, who previously served as chief operating officer, is now chief executive for the country’s largest nonprofit developer of urban mixed-income housing. TCB has developed 25,000 units of affordable and mixed-income housing at 320 properties in 15 states, including more than 6,500 units in Boston, where the company was founded.

Mitchell replaced Pat Clancy, who retired in December after 36 years with the company.

Mitchell’s involvement in community development began in the 1980s as an economic development and housing advisor to the mayor of Boston. He first joined TCB in 1989 as director of finance and went on to hold several senior-level development positions inside and outside of the company, before founding Mitchell Properties LLC in 2000. Mitchell returned to TCB in July 2010 as chief operating officer.

"Bart is an experienced executive with a passionate commitment to building and sustaining strong communities," said Philip L. Clay, chairman of the TCB board of directors. "He has the vision and expertise to advance TCB’s mission and position the company for successful growth."

"The Community Builders has been an innovator in mixed-income housing for nearly 50 years," said Mitchell. "I am excited and honored to lead our talented employees and dedicated residents into the future. Working together with our partners, we will continue to develop housing solutions that sustain communities."