Markwayne Mullin: What to know about the Oklahoma senator nominated to replace Kristi Noem

Sen. Markwayne Mullin picked as new DHS secretary

President Donald Trump on Thursday announced he would name Sen. Markwayne Mullin (R-OK) to be the next Secretary of Homeland Security. 

WASHINGTON - Following Kristi Noem’s ouster as Homeland Security Secretary on Thursday, President Donald Trump announced he would nominate Oklahoma GOP Sen. Markwayne Mullin.

Mullin is a staunch ally of Trump and a key disciple of the president during his 2024 campaign.

Here’s what to know about Mullin: 

Dig deeper:

Mullin is a rancher and business owner. He’s an enrolled member of the Cherokee Nation and is a former MMA fighter, according to his official website.

He spent 10 years in the House of Representatives before he became a senator in 2023.

During his time in Congress, he served on the Senate Armed Services, Appropriations, Health, Education, Labor and Pensions and the Indian Affairs Committees. 

FILE - U.S. Sen. Markwayne Mullin (R-OK) speaks during a Senate Committee on Health, Education, Labor, and Pensions hearing in the Dirksen Senate Office Building on Sept. 17, 2025 in Washington, DC. (Photo by Kevin Dietsch/Getty Images)

Mullins clashes with Teamsters

The backstory:

In 2023, Mullins and the president of the International Brotherhood of Teamsters President, Sean O’Brien, had an angry confrontation during a congressional hearing.

The conversation got so heated, Mullins challenged O’Brien to a fight, going so far as to stand up and take off his ring.

"This is the time, this is the place," Mullin told O’Brien after reading a series of critical tweets O’Brien had sent about him in the past. "If you want to run your mouth, we can be two consenting adults. We can finish it here."

RELATED: 'I don't want reality,' U.S. senator says as he grills panelist on race, children's books

Ethics investigation into Mullins’ business

In 2013, Mullins was faced with an ethics investigation after it was found he was still involved in his family business while serving the House. 

It was later concluded that Mullins made "good faith efforts" to comply with the committee’s guidance and was required to return $40,000 that was "mistakenly paid to him." 

Mullins supports Pete Hegseth

Mullins received backlash for his comments about his coworkers in January 2025, claiming senators have "shown up drunk" to vote on measures.

These comments came after claims of then-Defense Secretary nominee Pete Hegseth's alcohol abuse surfaced. Mullins continued to show unwavering support for the former FOX News co-host.