He attended private Catholic schools and served in the United States Marine Corps during the Korean War from 1951 to 1953.

Prior to entering politics, Manton was an officer of the New York City Police Department from 1955 to 1960[1] and served as a marketing representative for IBM from 1960 to 1964.

Manton ran in the Democratic primary for what was then a part of New York's 9th congressional district in northern Queens in 1978, following the retirement of 30-year incumbent James J. Delaney.

Tom Manton was the first major party chairman in the nation to endorse Bill Clinton for during the 1992 United States presidential election.

As the co-chairman of the Ad Hoc Committee on Irish Affairs in the House, he was instrumental in obtaining a visa for Gerry Adams to travel to the United States.

He withdrew on the last day it was legally possible to do so and arranged for his chosen successor, State Assemblyman Joseph Crowley, to replace him on the ballot.