Lake is the grandson of Kirsopp Lake, a member of the Church of England clergy who came from Oxford, England, to America in 1914 to teach New Testament studies at Harvard. Lake's father, Gerard Kirsopp Lake, was a New Deal Democrat, and his mother, Eleanor (née van Someren Hard), a Republican.
Lake himself was born in New York City. He attended Middlesex School and Harvard College, graduating with a Bachelor of Arts degree in 1961. Lake studied international economics at Trinity College, Cambridge for two years and later received a Ph.D from the Woodrow Wilson School of Public and International Affairs at Princeton University in 1974. He later (in 2001) co-edited a festschrift for his Princeton mentor, Richard H. Ullman.
Lake joined the State Department in 1962, serving until 1970 as a Foreign Service Officer. Lake was an assistant to Ambassador Henry Cabot Lodge, Jr. during the Vietnam War. His State Department career included assignments as consul at the US Embassy, Saigon, South Vietnam (1963), vice consul in Huế (1964–1965) and special assistant to the assistant to the president for national security affairs (1969–1970) in the Nixon administration. In 1969, he accompanied National Security Advisor Henry Kissinger on his first secret meeting with North Vietnamese negotiators in Paris. In 1970, he had a falling-out with Kissinger over the Nixon administration's Cambodian Campaign and left the State Department as a result. He later wrote a book critical of Kissinger's approach to Africa.
Lake worked for Democratic U.S. Senator Edmund Muskie of Maine in his 1972 presidential campaign. After Muskie lost the nomination to George McGovern, Lake served briefly at the Carnegie Endowment and International Voluntary Services before returning to serve as Director of Policy Planning under Jimmy Carter (1977–1981).
After Carter lost the 1980 election to Ronald Reagan, Lake became the Five College Professor of International Relations chair in Massachusetts (1981–1992), teaching first at Amherst College. In 1984, he moved to Mount Holyoke College, where he taught courses on the Vietnam War, Third World revolutions, and American foreign policy. (He left Mount Holyoke College in 1993 to become National Security Advisor from 1993 to 1997.) Among his protegees at Mount Holyoke was his student research assistant Mona Sutphen who would later serve in the Barack Obama White House as Deputy Chief of Staff for Policy. In 1997, he became Distinguished Professor in the Practice of Diplomacy at Georgetown University, until accepting his position with UNICEF.
During the 1992 presidential campaign, he was one of Clinton's chief foreign policy advisers. Lake later served as National Security Advisor (1993–1997). In the aftermath of the Cold War, Lake advocated a policy of "enlargement" of the number free market democracies. Told by the White House to sell his stocks in energy companies when he took the office in 1993, Lake did not do so. When Clinton decided in 1994 to allow Iran to arm the Bosnian army, Lake admitted he made a mistake when he didn't push to inform Congress of the decision.
Following Clinton's 1996 re-election, he nominated Lake to become the Director of Central Intelligence, but his nomination was withdrawn due to Republican opposition. It has also been reported that the failure of his nomination was related to his decision to withdraw support at the last minute for an Iraqi coup that might have removed Saddam Hussein without U.S. intervention. However, others have speculated that Lake's nomination "failed, in part, because Lake stated in a television interview that he was not sure if Alger Hiss was guilty."
After the withdrawal of his CIA nomination, Lake became White House Special Envoy (1998–2000). As special envoy Lake mediated the drafting of the Algiers Agreement, ending the Eritrean-Ethiopian War.
Lake co-founded Intellibridge Corporation in 2000 with David Rothkopf. In 2005 the assets of Intellibridge were acquired by the Eurasia Group.
Lake was a foreign policy adviser for Barack Obama's 2008 presidential campaign, having endorsed him over Senator Hillary Clinton, whom he had worked alongside during the Clinton administration. Lake was considered a potential Secretary of State until Senator Clinton was named to the position.
On March 16, 2010, Lake was named by United Nations Secretary General Ban Ki-moon as the next Executive Director of the United Nations Children’s Fund (UNICEF), following his nomination by U.S. President Barack Obama.
On April 30, 2010, he officially entered the post, succeeding Ann Veneman, a former U.S. Secretary of Agriculture. On 2 May 2014, he was reappointed Executive Director of UNICEF by United Nations Secretary-General Ban Ki-moon.
At UNICEF, he has been active at effort to refocus investment towards the most disadvantaged children, and reducing child mortality.
Lake was an advisory board member for the Partnership for a Secure America, a not-for-profit organization dedicated to recreating the bipartisan center in American national security and foreign policy. He has also served as chair on the boards of the United States Fund for UNICEF and the Marshall Legacy Institute. He also is serving a term from 2005-2010 on the Mount Holyoke College Board of Trustees.
For many years Lake served on the Board of Trustees for St. Mary's College of Maryland. He played key roles in the establishment of the Center for the Study of Democracy at the college, where he also served on the advisory board.
Lake was raised in the Congregational Church, but recounts that he "embarked on his spiritual journey as a young man," first converting to the Episcopal Church. However, since then he had "long been drawn to Judaism," and "began to feel strongly that I wanted to be part of that community." He ultimately converted to Judaism in 2005, before marrying Julie T. Katzman, currently the Executive Vice President and Chief Operating Officer of the Inter-American Development Bank. He credits Katzman's religious faith as the impetus responsible for his decision to investigate his attraction to Judaism more fully, and began studying with former Navy Chaplain Rabbi Arnold Resnicoff (who was serving with him on the Board of Trustees of the Carnegie Council for Ethics in International Affairs) for a full year before his conversion. Later, Resnicoff officiated at his marriage to Katzman.
However, Lake jokes that he was Jewish in the eyes of others well before his formal conversion. First, in 1997, when news broke that Secretary of State Madeleine Albright had discovered that she had Jewish ancestors, and a story about other Jews in the Administration mistakenly reported that Clinton's "entire national security team was Jewish." Based on that news story, Lake recounts, his name was added to the list used by the White House Liaison to the Jewish community, and Lake began to receive invitations to special events, such as the White House Hanukkah Party—and he says he was delighted to accept those invitations. The second time was two years later, when a 1999 Washington Post story described a new release of Watergate tapes of conversations between President Richard Nixon and H.R. Haldeman, his Chief of Staff. Those tapes included a conversation where Nixon asks if Lake is Jewish, and Haldeman responds, "Well, I'm not so sure, but he looks Jewish." Based on these tapes, Lake has said that, "Now I can trace my [Jewish] heritage all the way back to Nixon!"
Lake has three children, from his marriage to his first wife, Antonia, which ended in 1995.
Books authoredMore Than Humanitarianism : A Strategic U.S. Approach Toward Africa (2006, co-author with Christine Todd Whitman)
6 Nightmares: The Real Threats to American Security (2001)
The Real and the Ideal: Essays on International Relations in Honor of Richard Ullman (2001, co-edited)
After the Wars: Reconstruction in Afghanistan, Central America, Indochina, the Horn of Africa, and Southern Africa (1990, editor)
Somoza Falling: A Case Study of Washington at Work (1989)
Third World Radical Regimes: U.S. Policy Under Carter and Reagan (1985)
Our Own Worst Enemy: The Unmaking of American Foreign Policy (1984, co-author)
The "Tar Baby" Option: American Policy Toward Southern Rhodesia (1976).
Legacy of Vietnam: The War, American Society, and the Future of U.S. Foreign Policy (1976, contributing editor)