His father, Judge Charles J. Vallone (1901–1967) of the Queens County Civil Court, encouraged young Peter to broaden his horizons beyond the limited social interactions with other ethnic and religious groups that were discouraged in the pre-Vatican II era.
Vallone drafted changes to the City Charter in 1989 that he claimed allowed the Council more say on the budget.
He was an unsuccessful candidate for governor in 1998 as the Democratic nominee receiving in total 1,570,317 votes or 33.16% of the electorate.
He practices law in Astoria with his son, Peter Vallone Jr., who succeeded him in the City Council in 2002.
In 2009, he endorsed a former rival in the mayoral race, Mark Green, who attempted to win back the job of Public Advocate.