[4] Mitchell went to Iraq in 2003 to work for British kidnap and ransom risk-management company Control Risks, providing security to officials of the Coalition Provisional Authority government.

The company set up subsidiary Threat Management Group, with Mitchell as CEO and shareholder, to improve security for its logistics staff.

[3][7] The company took on contracts protecting infrastructure and Mitchell dealt with kidnap and ransom negotiations in Iraq, Afghanistan, Somalia and Darfur.

[13] During the 2017 general election, Mark Mitchell was re-elected in the Rodney electorate, defeating Labour candidate Marja Lubeck by a margin of 19,561 votes.

[20] During the 2020 general election, Mitchell won the seat of Whangaparāoa (which had replaced his previous electorate of Rodney) by a final margin of 7,823 votes.

"[26] In August 2023, Mitchell said that these military academies would be modelled after the New Zealand Defence Force's six-week Limited Service Volunteer programme.

[28] During the 2023 New Zealand general election, Mitchell was re-elected in Whangaparāoa by a margin of 23,376, defeating Labour's candidate Estefania Muller Pallarès.

[32] On 21 February 2024, Mitchell participated in a Newstalk ZB interview with Labour MP Ginny Andersen that was hosted by Mike Hosking.

When Mitchell talked about his work as a private security contractor in Iraq in 2004, Andersen asked if he had been "paid to kill people" in his previous career.

Though Andersen initially defended her remarks on free speech grounds, she apologised after Labour Party leader Chris Hipkins expressed disapproval of her comments.

Mitchell questioned the sincerity of Andersen's apology and turned his attention to expressing condolences for the recent death of late Green MP Efeso Collins, which occurred that same day.

"[34] On 6 May 2024, Mitchell and Prime Minister Christopher Luxon announced that the Government would allocate NZ$1.9 billion from the upcoming 2024 New Zealand budget to training 470 new corrections officers and adding 810 beds to Waikeria Prison.

Green Party justice spokesperson Tamatha Paul defended the provisions and criticised the high Māori incarceration rate as a violation of the Treaty.

In response, Mitchell stated that a review of Treaty principles in legislation was part of the Government's coalition agreement and argued that it did not affect Corrections' engagement with Māori families and hapū.

[37] As a senior cabinet minister, Mitchell represented New Zealand at the Summit on Peace in Ukraine at Bürgenstock Resort in Switzerland on 15–16 June 2024.