Jeffrey David Klein was born in the Morris Park section of the Bronx on July 10, 1960. A lifelong resident of the northeast Bronx, he was educated in Bronx public schools. Klein received a B.A. with honors from Queens College, an M.P.A. from Columbia University, School of International and Public Affairs, and a J.D. from the City University of New York Law School where he was a member of the law review. Jeffrey has over 15 years experience practicing personal injury law.

A former chief of staff to Congressman James Scheuer, Klein served as a Democratic State Committeeman and District Leader before being elected to the New York State Assembly in 1994. During his ten years representing the 80th Assembly District in the state legislature, Jeff Klein served as Chairman of the Subcommittee on Crime and the Elderly, the Committee on State-Federal Relations, and the Committee on Oversight, Analysis and Investigations. In November 2004, Senator Klein was elected to represent the 34th Senatorial District covering parts of northern Bronx County and southern Westchester County.