Pignatelli entered politics in 1987 when he was elected to the Lenox Planning Board.

He also served as a Berkshire County Commissioner from 1995 to 1999, including two years as Chairman.

[1] In 2002, Pignatelli was elected to the Massachusetts House of Representatives, defeating fellow Lenox resident Kevin J. Sherman by 106 votes in the Democratic primary and winning the general election with 50.2% of the vote against two candidates.

[2] As of 2023, Pignatelli represents the towns of Alford, Becket, Egremont, Great Barrington, Lee, Lenox, Monterey, Mount Washington, New Marlborough, Otis, Richmond, Sandisfield, Sheffield, Stockbridge, Tyringham, Washington and West Stockbridge, all in Berkshire County.

[1] On February 6, 2024, Pignatelli announced he would not seek reelection after eleven terms.