Political career
Teo made his political debut in the 1992 by-elections in Marine Parade GRC as part of a four-member PAP team led by Prime Minister Goh Chok Tong. After the PAP team won 72.9% of the vote against three opposition parties, Teo was elected as the Member of Parliament (MP) representing the Joo Chiat ward of Marine Parade GRC. He was subsequently appointed as Minister of State for Finance, Minister of State for Communications and Minister of State for Defence.
In April 1995, Teo was appointed as Senior Minister of State for Defence and Acting Minister for the Environment. In January 1996, he was promoted to full Minister and given the Cabinet portfolios of Minister for the Environment and Second Minister for Defence.
Teo switched to contesting in Pasir Ris GRC during the 1997 general election and the four-member PAP team led by him won 70.9% of the vote against the Workers' Party. Teo thus elected as the MP representing the Pasir Ris Loyang ward of Pasir Ris GRC. In subsequent Cabinet reshuffles, he became Minister for Education while continuing to serve as Second Minister for Defence.
During the 2001 general election, Teo led the five-member PAP team contesting in the newly formed Pasir Ris–Punggol GRC and won an uncontested walkover. After winning the general election, he continued to hold his previous Cabinet portfolios while becoming the MP representing the Pasir Ris West ward of Pasir Ris–Punggol GRC. On 1 August 2003, Teo was appointed as Minister for Defence and Minister-in-charge of the Civil Service.
During the 2006 general election, Teo led a six-member PAP team to contest in Pasir–Ris Punggol GRC again and won 68.7% of the vote against the Singapore Democratic Alliance. He retained his parliamentary seat and continued holding his Cabinet portfolios. On 1 April 2009, Teo was appointed as one of two Deputy Prime Ministers, in addition to his portfolios as Minister for Defence and Minister-in-charge of the Civil Service.
Teo led a six-member PAP team to contest in Pasir–Ris Punggol GRC in the 2011 general election and won 64.79% of the vote against the Singapore Democratic Alliance. On 18 May 2011, Teo relinquished his Cabinet portfolio of Minister for Defence and took up the positions of Minister for Home Affairs and Coordinating Minister for National Security, while concurrently serving as Deputy Prime Minister and Minister-in-charge of the Civil Service.
On 1 May 2019, Teo relinquished his appointment as Deputy Prime Minister to become a Senior Minister, while retaining his position as Coordinating Minister for National Security. In his new role, he also oversaw four departments under the Prime Minister's Office; Smart Nation and Digital Government Group, National Security Coordination Secretariat, National Population and Talent Division, and the National Climate Change Secretariat.
On 21 April 2025, Teo announced that he will not be contesting for the Pasir Ris–Changi GRC in the 2025 general election.
On 23 April, on the Nomination Day for the 2025 general election, Teo was not nominated as a candidate for any constituencies. Prime Minister Lawrence Wong later then announced Teo's retirement from politics in a Facebook post. Teo was then appointed Senior Advisor in the Prime Minister's Office.
