Five things to know about Oklahoma Senator Markwayne Mullin, Trump’s choice for new DHS secretary

Sen. Markwayne Mullin, R-Okla., speaks to reporters following a weekend vote to move forward with a stopgap funding bill to reopen the government through Jan. 30, at the Capitol in Washington, Monday, Nov. 10, 2025.J. Scott Applewhite/Associated Press

President Trump on Thursday fired DHS Secretary Kristi Noem and announced he was replacing her with Oklahoma Senator Markwayne Mullin.

Here’s a quick primer on the Oklahoma Republican.

A lawmaker

Mullin is serving his first term in the US Senate, which began in January 2023, according to his official biography. Before that he spent 10 years as an Oklahoma congressman.

A grappler

Mullin attended Missouri Valley College on a wrestling scholarship until the age of 20, his biography says.

When his “father, Jim, fell ill ... Mullin and his recent bride Christie postponed studies to save the family business, Mullin Plumbing,” his bio says.

A businessman

The plumbing concern continues to thrive, the biography states.

“Over the past 28 years, Markwayne and Christie Mullin have expanded Mullin Plumbing to become the largest service company in the region, and along the way founded numerous other successful companies, ranging from Mullin Environmental to Rowan’s Steakhouse,” the bio states.

A family man and a rancher

Mullin and his wife have “six wonderful children,” the bio says.

“A lifelong Oklahoman, Senator Mullin grew up on his family’s ranch in Westville where he and his family still reside to this day,” the bio states.

A spat with a union boss

Mullin made headlines back in 2023 when he clashed with Teamsters boss Sean O’Brien during a testy hearing before the Senate Committee on Health, Education, Labor & Pensions.

Mullin noted that O’Brien had insulted him several times on social media, calling him a “greedy CEO who pretends like he’s self-made,” as well as a “clown” and a “fraud.”

“Sir, this is a time, this is a place. You want to run your mouth, we can be two consenting adults, we can finish it here,” Mullin said to O’Brien, a witness at the hearing.

“OK, that’s fine. Perfect,” O’Brien fired back.

Sean O’Brien, the general president of the International Brotherhood of Teamsters, announced that he’s running for reelection at a Charlestown rally in Boston on January 16.Pat Greenhouse/Globe Staff

“You want to do it now?” Mullin asked. “Stand your butt up then.”

“You stand your butt up,” O’Brien retorted.

At that point, Mullin sprang from his chair and adjusted his wedding ring as if preparing to remove it for a bareknuckle scrap, while others could be heard yelling.

Senator Bernie Sanders quickly interceded, telling Mullin to “hold it” and “sit down.”

“No, no, no, sit down. Sit down! You’re a United States senator, sit down,” Sanders said. He banged his gavel. No blows were exchanged.