Jayakumar served as Singapore's Permanent Representative to the United Nations and High Commissioner to Canada from 1971 to 1974, and was a member of Singapore's delegation to the UN Law of the Sea Conference from 1974 to 1979. Jayakumar authored three books and 32 articles on the topics of constitutional law, international law and legal education. He was awarded the Public Service Star in 1980. In 1980, Jayakumar was elected a member of parliament for the constituency of Bedok. He was returned as the MP for the same constituency in 1984 as an incumbent, and as one of the three MPs in the newly created Group Representation Constituency scheme in 1988. This was again the case, as one of the four MPs in the same GRC in the 1991 General Election. He was re-elected as one of six MPs for the East Coast GRC in the 1997 General Election. In 2006, he was re-elected in the new five-member East Coast GRC. In 1981, Jayakumar was appointed as a Minister of State at the Ministry of Home Affairs and Ministry of Law. He entered the Cabinet of Prime Minister Lee Kuan Yew in 1984 as the Minister for Labour with the additional portfolios of Second Minister for Home Affairs and Second Minister for Law. Jayakumar was appointed Minister for Home Affairs and Second Minister for Law on January 2, 1985. In 1988, Jayakumar was appointed Minister for Law and Minister for Home Affairs. He retained these portfolios when Goh Chok Tong became Prime Minister in 1990. In January 1994, Jayakumar was appointed Minister for Foreign Affairs and Minister for Law. On 12 August 2004 when it was his 65th birthday, Jayakumar was appointed Deputy Prime Minister and Minister for Law in the Cabinet of the new Prime Minister, Lee Hsien Loong. On 1 September 2005, Jayakumar took over the role as Co-ordinating Minister for National Security from former President Tony Tan to oversee counter-terrorism policies in Singapore. Jayakumar stepped down as Minister for Law on April 30, 2008, and as Deputy Prime Minister on April 1, 2009.
Retirement
Jayakumar was appointed a Senior Minister on April 1, 2009 before retiring from politics on May 21, 2011. He decided not to contest in the 2011 General Elections due to health reasons. After retirement, he served as Chair of the National University of Singapore Faculty of Law's Advisory Council and Patron of the NUS Centre for International Law. He is also presently a consultant with Drew & Napier. In 2015 he published a memoir titled 'Be at the Table or Be on the Menu: A Singapore Memoir'. He is currently appointed as a pro-chancellor of the National University of Singapore for a three year term starting from July 1, 2020.