Senator Greenstein is the first woman to represent the 14th Legislative District in the Senate, which includes Cranbury, Jamesburg, Monroe, Plainsboro and Spotswood in Middlesex County and East Windsor, Hamilton, Hightstown and Robbinsville in Mercer County.

A fulltime Legislator, Senator Greenstein serves as Assistant Majority Leader of the State Senate as well as Chairwoman of the Law and Public Safety Committee. Senator Greenstein also serves as Vice-Chairwoman of the Environment and Energy Committee and as a member of the Senate Budget and Appropriations Committee and the Joint Committee on the Public Schools.

Senator Greenstein was educated at Vassar College, Johns Hopkins University, and the Georgetown University Law Center and is a specialist in disability law. Prior to becoming a legislator, she was a Senior Staff Attorney at the Community Health Law Project and served as a Deputy Attorney General in the Division of Criminal Justice in Trenton and as an Assistant District Attorney in Philadelphia. She also served as a Clinical Associate Professor at Seton Hall Law School.

During her ten-years in the General Assembly, then-Assemblywoman Greenstein served in a number of leadership roles. She was appointed Deputy Speaker of the General Assembly in 2006, following a four-year period serving as Assistant Majority Leader. She Chaired the Assembly Judiciary Committee and was a member of the Assembly Health and Senior Services Committee.

Senator Greenstein has a strong legislative track record of protecting New Jersey's children and families. She was a prime sponsor of Caylee's Law, which makes it a felony for failing to report the disappearance of a child within 24 hours; sponsored legislation expanding Megan's Law, protecting children from known sex offenders; and authored Jessica Rogers' Law which protects New Jerseyans against drivers with road rage. Senator Greenstein is a prime sponsor of New Jersey's Paid Family Leave Law, which allows workers to apply for up to six weeks of paid leave to care for a newborn or newly adopted child, or a sick parent, spouse or child. She has also authored legislation to increase school bus safety.

Senator Greenstein has supported efforts to decrease the state's reliance on fossil fuels by promoting electric cars and has advocated for making clean and renewable energy a priority for New Jersey by increasing the state's renewable energy portfolio.

Senator Greenstein is the author of New Jersey's tough anti-telemarketing law. She has also sponsored legislation calling for a State Constitutional Convention for property tax reform.

Senator Greenstein has recently been honored with the New Jersey Jewish War Veterans Legislator of the Year Award and with the New Jersey State AFL-CIO's Legislator of the Year Award. In the past she has been named Legislator of the Year for numerous organizations including the AARP and the New Jersey Police Benevolent Association.

Senator Greenstein has served as an elected member of West-Windsor Plainsboro School Board and as Vice President of the Mercer County School Boards Association. She was also an elected member of the Plainsboro Township Committee prior to becoming a Legislator. She is currently a member of the Boy Scouts of America - Central New Jersey Council Advisory Board. In the past, Senator Greenstein has served as a Trustee of Angel's Wings - a Mercer County-based social service agency - and as a board member of the New Jersey Council for the Humanities.

Senator Greenstein is the chair of the manufacturing caucus.