Matthew Nimetz was born in New York City to a Jewish familyand educated at Williams College where he received a B.A. in 1960. He subsequently was a Rhodes Scholar and received a B.A. from Balliol College, Oxford in 1962. He got his LL.B. from Harvard Law School in 1965.,where he was President of the Harvard Law Review. He returned to Balliolfor a M.A., granted 1966.
He served as law clerk to Supreme Court Justic Marshall Harlan II from 1965 to 1967, before serving as a staff assistant to IS President Lyndon B. Johnson until 1969. He worked with the New York City law firm Simpson, Thatcher & Bartlett as an associate from 1969 to 1973 and partner from 1974 to 1977. He also directed the transition of Governor-Elect Hugh Carey of New York in 1974-5, and was a commissioner of the Port Authority of New York and member of the New York Health Advisory Council from 1975 to 1977.
In January 1977 Nimetz was appointed by President Jimmy Carter as Counselor of the United States Department of State. In that capacity he provided advice to Secretary of State Cyrus Vance and had special responsibilities in connection with the Cyprus issue, Eastern Mediterrean issues including Greek-Turkish disputes, implementation of the Helsinki Final Act and other issues involving Eastern/Central Europe, U.S.-Mexican border issues, the Micronesian status negotiations, and other matters. In December 1979, he was promoted to the post of Under Secretary for Security Assistance, Science and Technology.He was responsible for the supervision of United States security assistance programs and the implementation of the State Department's international scientific and technological programs. These included areas such as scientific and technical cooperation, nuclear nonproliferation issues, environmental matters, and the US Government's international communications activities. He was also responsible for supervising US policy on the eastern Mediterranean and eastern European countries.
After the end of the Carter Administration in January 1981, Nimetz returned to the private sector. He became a partner in the New York law firm Paul, Weiss, Rifkind, Wharton & Garrison, where he concentrated in corporate and international law. He moved to the private equity investment firm General Atlantic in January 2000, where he is a managing director and Chief Operating Officer. In May 2007 he was again appointed as a Commissioner of the Port Authority of New York by Governor Elliott Spitzer but, upon the resignation of Governor Spitzer, his nomination was not acted upon for confirmation by the State Senate.
From March 1994 to September 1995, he served as President Bill Clinton's Special Envoy to mediate the resolution of the Macedonia naming dispute.This effort culimated in the signing of the Interim Agreement of September 13, 1995 by Greece and the Republic of Macedonia at the United Nations which resolved many of the issues between the two countries. He became a deputy to Cyrus Vance, a former United States Secretary of State who served as Personal Envoy of the United Nations Secretary General in the talks on the remaining open issues in the dispute, in particular the name of the country. He chaired those talks from November 1997 onwards - as that Personal Envoy, from Vance's resignation from that position in December 1999, appointed in turn by Kofi Annan and Ban Ki-moon.
Nimetz has been a director of The Nature Conservancy of New York, trustee and founding chair of World Resources Institute, trustee emeritus of Williams College, trustee of Central European University, Budapest, and of the Committee for Economic Development.
As of 2009, he is an advisory director of The Levin Institute of the University of the State of New York,and a memberand founding (former) chair of the Centre for Democracy and Reconciliation in Southeastern Europe.