William F. Weld, the former governor who left Boston to practice law and delve into venture capital in New York for the last 15 years, is returning to Massachusetts to become a partner in one of the city’s largest law firms, and consultant to its lobbying arm.

Weld will become a partner at Mintz Levin, and also a principal at ML Strategies, the law firm’s government relations affiliate. He will focus on serving both international and domestic clients with legal and strategic advice.

“He’s energized and excited to be back in Boston,’’ said a source close to the law firm.

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He will join Stephen Tocco, his former top Cabinet secretary who also served as chief executive director of the Massachusetts Port Authority.

Tocco and Robert Popeo, the law firm’s chairman, put together the agreement for Weld’s return to Boston.

The former governor, who served from 1991 to 1997, will relocate with his wife, Leslie, to Cambridge.

Weld, a Republican and one of the state’s most popular governors in recent times, resigned in 1997 after President Clinton nominated him to be ambassador to Mexico. The Senate ultimately blocked his appointment.

The law firm is expected to release an announcement of Weld’s hiring late this afternoon.

Since leaving government, Weld has been affiliated with McDermott Will & Emery in New York.