[2] His mother was elected to the Parliament of Victoria in 1987 and served as a state government minister, while his father was a country vice-president of the Liberal Party of Australia (Victorian Division).

He was encouraged to run for Liberal preselection by Denis Napthine, a family friend, and beat nine other candidates in the ballot despite his lack of prior connections with the area.

[6] In February 2015, Tehan publicly supported Prime Minister Tony Abbott in the lead-up to a motion to spill the leadership of the Liberal Party.

[11] In the fourth rearrangement of the same Turnbull ministry, on 20 December 2017 Tehan was promoted to the Minister for Social Services and served as a member of the Cabinet.

[12] During the August 2018 Liberal leadership spills, Tehan announced that he would not vote to depose a sitting prime minister.

[16] The first, led by Robert French, recommended the adoption of a freedom-of-speech code, with universities agreeing to implement this by the end of 2020.

[19] Tehan was moved to the trade portfolio in a December 2020 cabinet reshuffle, prompted by the retirement of Mathias Cormann.

[5] Following the Coalition's defeat at the 2022 federal election, Tehan was given the immigration and citizenship portfolio in Peter Dutton's shadow cabinet.

[22] Tehan opposed the legalisation of same-sex marriage in Australia, but in June 2016 announced he would vote in parliament in accordance with the results of a nationwide plebiscite.