He attended The Catholic University of America before graduating from Columbia University in 1978 and later earned a law degree from the Georgetown University Law Center in 1981 and a master's degree in education from Harvard University in 1982.

McGreevey was a member of the New Jersey General Assembly from 1990 to 1992, when he became Mayor of Woodbridge Township, New Jersey. He was re-elected mayor in 1995 and 1999. He was elected to the New Jersey Senate in 1993, simultaneously serving as mayor during the four-year Senate term. He first ran for governor in 1997, but was defeated in a close race (47%-46%) by the incumbent Republican, Christine Todd Whitman, with Libertarian candidate Murray Sabrin taking slightly over 5% of the vote. McGreevey ran for the governorship again in 2001 and won. His Republican opponent in that race was Bret Schundler, who began to campaign after Donald DiFrancesco dropped out of the race due to allegations of corruption.

After being elected to the governorship on his second try (on November 6, 2001), McGreevey inherited a $5 billion budget deficit. During his term, McGreevey fought tax increases for most residents of the state, although he did eventually raise the tax on cigarettes and increased the state tax rate for the higher incomes.

McGreevey, of Irish descent, was raised as a Roman Catholic. Due to his pro-choice stance on abortion, he stated as governor that he would not receive Communion at public church services. This decision came after a request by Archbishop John J. Myers of the Archdiocese of Newark for pro-choice supporters to not seek communion when they attended mass. McGreevey is committed to the separation of church and state, having said that he believes "it's a false choice in America between one's faith and constitutional obligation."[1] McGreevey implemented a stem cell research plan for New Jersey, and heavily lobbied for the state's first domestic partnership law for same-sex couples, which he signed into law in early 2004. Because he remarried without an annulment from his first marriage, Bishop Joseph A. Galante of the Diocese of Camden said that he would refuse communion to McGreevey if he attended his installation as bishop. Since leaving office, McGreevey has joined an Episcopal church, which he attends regularly. [2]

McGreevey has one daughter from his first marriage to Kari Schutz, which ended in divorce, and one daughter from his second marriage to Dina Matos, from whom McGreevey is now separated. The two are in the process of divorcing.

McGreevey has been dating an Australian-born excecutive, Mark O'Donnell, since late 2005. The New York City-area media reported in April 2006 that the couple were planning to buy a house together in Plainfield, New Jersey.