Blix was born in Uppsala, Sweden. He is the son of professor Gunnar Blix and Hertha Wiberg, and grandson of professor Magnus Blix. He comes from a family of Jamtlandic origin. Blix studied at Uppsala University and Columbia University, earning his PhD from the University of Cambridge (Trinity Hall). In 1959, he earned a Juris Doctor in International Law at Stockholm University, where he was appointed Associate Professor in International Law the next year. Hans Blix has two sons, Mårten and Göran, who both have doctoral degrees.
Between 1962 and 1978 Blix was a member of the Swedish delegation at the Disarmament Conference in Geneva. He held several other positions in the Swedish administration between 1963 and 1976, and from 1961 to 1981 served on the Swedish delegation to the United Nations. From 1978 to 1979, Blix was the Swedish Foreign Minister.
Blix chaired the Swedish Liberal Party's campaign during the 1980 referendum on nuclear power, campaigning in favour of retention of the Swedish nuclear energy program.
Blix became Director General of the International Atomic Energy Agency between 1981 and 1997 after Sigvard Eklund.
Blix personally made repeated inspection visits to the Iraqi nuclear reactor Osiraq before its attempted destruction by the Iranians, in 1980, and its eventual destruction by the Israeli Air Force in 1981 during Operation Opera. Although most agreed that Iraq was years away from being able to build a nuclear weapon, the Iranians and the Israelis felt any raid must occur well before nuclear fuel was loaded to prevent nuclear fallout. The attack was regarded as being in breach of the United Nations Charter (S/RES/487) and international law and was widely condemned. Iraq was alternately praised and admonished by the IAEA for its cooperation and lack thereof. It was only after the first Gulf War that the full extent of Iraq's nuclear programs, which had switched from a plutonium based weapon design to a highly enriched uranium design after the destruction of Osiraq, became known.
Another significant event during his time as head of the IAEA was the Chernobyl disaster on 26 April 1986, a nuclear accident rated at the highest level 7 on the IAEA's International Nuclear Event Scale.
During the Iraq disarmament crisis before the 2003 invasion of Iraq, Blix was called back from retirement by UN Secretary General Kofi Annan to lead the United Nations Monitoring, Verification and Inspection Commission in charge of monitoring Iraq. Kofi Annan originally recommended Rolf Ekéus, who worked with UNSCOM in the past, but both Russia and France vetoed his appointment.
Blix personally admonished Saddam for "cat and mouse" games and warned Iraq of "serious consequences" if it attempted to hinder or delay his mission.
In his report to the UN Security Council on 14 February 2003, Blix claimed that "so far, UNMOVIC has not found any such weapons [of mass destruction], only a small number of empty chemical munitions."
In 2004 Blix gave a statement that "there were about 700 inspections, and in no case did we find weapons of mass destruction."
Blix's statements about the Iraq WMD program came to contradict the claims of the George W. Bush administration, and attracted a great deal of criticism from supporters of the invasion of Iraq. In an interview on BBC 1 on 8 February 2004, Blix accused the US and British governments of dramatizing the threat of weapons of mass destruction in Iraq, in order to strengthen the case for the 2003 war against the government of Saddam Hussein. Ultimately, no stockpiles of weapons of mass destruction were ever found.
In an interview with The Guardian newspaper, Blix said, "I have my detractors in Washington. There are bastards who spread things around, of course, who planted nasty things in the media."
In 2004, Blix published a book, Disarming Iraq, where he gives his account of the events and inspections before the coalition began its invasion.
Senior U.S. officials ordered the U.S. Central Intelligence Agency (CIA) to investigate Blix to gather "sufficient ammunition to undermine" him so that the U.S. could start the invasion of Iraq. The U.S. officials were upset that the CIA did not uncover such information.
Blix said he suspected his home and office were bugged by the United States, while he led teams searching for Saddam Hussein's supposed weapons of mass destruction. Although these suspicions were never directly substantiated, evidence of bugging of UN security council representatives around the time the US was seeking approval from the council came to light after a British government translator leaked a document "allegedly from an American National Security Agency" requesting that British intelligence put wiretaps on delegates to the UN security council.
Since 2003 Blix has been chairman of the Weapons of Mass Destruction Commission (WMDC), an independent body funded by the Swedish government and based in Stockholm.
In December 2006, the Weapons of Mass Destruction Commission said in a report that Pakistan's nuclear scientist Abdul Qadeer Khan could not have acted alone when passing on nuclear data and designs "without the awareness of the Pakistan government."
In 2009 Blix joined the project Soldiers of Peace a movie against all wars and for a global peace.
Blix chairs a panel of advisors who oversee the establishment of the UAE's Dh150 billion atomic energy programme. He leads the nine-person board, which meets twice a year. The International Advisory Board (IAB) oversees progress of the nation's nuclear energy plan and issue reports on potential improvements to the scheme.Doctorate Honoris causa of the University of Moscow in 1987.
Recipient of the Henry DeWolf Smyth Nuclear Statesman Award in 1988.
Honorary membership in the Cambridge Union Society.
Gold Medal for distinguished service in the field of nuclear affairs by the Uranium Institute (now World Nuclear Association) in 1997.
Otto Hahn Prize of the City of Frankfurt/Main in 1998.
Doctorate Honoris causa of the Vrije Universiteit Brussel in 2003.
Commander of the Légion d'Honneur in 2004.
Doctorate Honoris causa of the University of Padova in 2004.
Sydney Peace Prize in 2007.
Doctorate Honoris causa of the University of Cambridge in 2007.
Elected as Honorary President of the World Federation of United Nations Associations in 2009. Elected as President of the World Federation of United Nations Associations in Buenos Aires in 2006 and served until 2009.
Awarded the Fulbright Prize in 2014.
Blix is parodied in Team America: World Police, where North Korean dictator Kim Jong-il feeds him to nurse sharks after Blix threatens him with an angry official letter.
Blix also appeared in the documentaries The World According to Bush, and Europe & USA: Behind the Scenes of a Political Rupture.