President Donald Trump said Thursday he is replacing Homeland Security Secretary Kristi Noem and will nominate Oklahoma Sen. Markwayne Mullin to run the department that oversees border security, immigration enforcement, disaster response and transportation screening.
The shake-up comes after days of intense hearings on Capitol Hill and a widening dispute over a costly federal advertising campaign that featured Noem. It also lands as the Department of Homeland Security remains partly shut down in a funding fight with Congress, leaving tens of thousands of workers furloughed or working without pay. Trump said Mullin would begin March 31, and he said Noem will move into a new role as a special envoy tied to what he called “The Shield of the Americas,” an initiative he said will focus on the Western Hemisphere.
Trump announced the change on social media, calling Mullin “highly respected” and thanking Noem for her service. The White House did not immediately release a formal resignation letter from Noem or a separate statement describing why she was being moved. The post said Mullin would take over at the end of the month, which would leave Noem in office until then unless Trump changes course. The Homeland Security secretary is a position that requires Senate confirmation, and the administration said it plans to send Mullin’s nomination to the Senate. The Department of Homeland Security, created after the Sept. 11 attacks, has about 260,000 employees and includes Immigration and Customs Enforcement, Customs and Border Protection, the Transportation Security Administration, the Federal Emergency Management Agency and the Secret Service.
Noem, a former South Dakota governor, has been one of the most visible faces of Trump’s immigration push. She traveled with enforcement teams and regularly posted tough messages about deportations and arrests. Under her leadership, immigration agents carried out street-level sweeps in major cities, including operations that drew protests in neighborhoods and outside federal buildings. Supporters said the approach was needed to restore order at the border and speed up removals. Critics said the tactics were too broad, swept up people with no criminal record and fueled fear in immigrant communities.
The president’s decision followed a week in which Noem faced sharp questioning from both parties in Congress. Lawmakers pressed her on the department’s enforcement tactics and on several controversies that have piled up since the start of Trump’s second term. In Senate and House hearings this week, she was challenged about a federal ad campaign meant to promote the administration’s border message. The ads placed Noem front and center, and lawmakers questioned the contract process and why so much money was spent on a media blitz during a time of tight budgets and deep agency strain.
Trump added fuel to that dispute in a separate interview when he said he did not know about the ad campaign and did not approve it. That claim directly undercut Noem’s testimony to lawmakers that the president supported the effort. The fight over who signed off on the spending became a major issue during her appearances on the Hill, and it turned into a fresh test of trust inside an administration that prizes loyalty. The White House did not say whether the ad dispute was the main reason for Trump’s move, but it came as Republicans and Democrats alike demanded answers about how the contract was awarded and why the department chose an approach that seemed designed to feature the secretary herself.
Noem was also under heavy fire over her response to an incident in Minnesota earlier this year in which federal immigration officers shot and killed two U.S. citizens during an operation. In the immediate aftermath, Noem publicly described the deaths as “domestic terrorism,” a characterization that drew backlash after videos circulated and raised questions about what happened in the moments before the shootings. The episode helped trigger calls for her removal and, from House Democrats, a push to begin impeachment proceedings. Some Republican lawmakers also criticized her handling of the matter and said the department needed clearer guardrails for enforcement operations.
At the same time, the department has been caught in a broader political standoff that has disrupted normal operations. Some DHS functions have been limited for weeks because of a budget impasse tied to immigration policy demands. In public testimony, Noem acknowledged that about 100,000 DHS workers were furloughed, while other employees, including those tied to airport screening and travel security, continued working without pay. Lawmakers from both parties have pressed for changes that would require immigration officers to use body-worn cameras more widely, and Democrats have sought limits on when agents can enter homes without a judge-signed warrant. Noem said she wanted funding for cameras but argued the department could keep using administrative warrants in most cases.
Mullin, 48, is a Republican who served a decade in the U.S. House before he was elected to the Senate in 2022. A business owner and rancher from eastern Oklahoma, Mullin has styled himself as a blunt, combative defender of Trump’s agenda. In the Senate, he has served on major committees, including Armed Services and Health, Education, Labor and Pensions, and he has been a regular presence in hearings that touch national security and border issues. Trump did not say Thursday whether Mullin’s main mission would be to intensify the current deportation strategy, shift to more targeted operations, or change the department’s leadership team.
If the Senate confirms Mullin, his move would also create a vacancy in one of Oklahoma’s Senate seats. State rules would govern how that seat is filled, and the process could include a temporary appointment followed by an election. For Trump, putting a sitting senator into a Cabinet job would also test how quickly his allies can move a nomination through a Senate that has been consumed by fights over immigration, spending and oversight. The administration did not say when Mullin’s confirmation hearing would be scheduled, and Senate leaders did not immediately announce a timeline.
Trump said Noem will become “Special Envoy for The Shield of the Americas,” which he described as a new security initiative focused on the Western Hemisphere that will be announced Saturday in Doral, Florida. The White House has not provided details on what the initiative would include, how it would be funded, or how it would overlap with existing security and immigration programs across the region. It was also not clear what authority the envoy role would carry, whether it would require Senate confirmation, or how Noem’s office would work with the State Department, the Pentagon and DHS. Noem did not immediately make a public statement of her own about the move.
For now, the change leaves DHS in a transition period during an active policy fight, with key deadlines approaching for funding and for the next round of immigration enforcement planning. Trump’s announcement sets up a fast-moving month in which Noem remains in office, Mullin prepares for a confirmation process, and lawmakers keep pressing the department for records tied to spending decisions and enforcement actions.
As of Thursday, March 5, Noem remained the Homeland Security secretary, Mullin had not yet been confirmed, and the next major milestone Trump cited was the planned March 8 announcement in Doral of the administration’s “Shield of the Americas” initiative.
Author note: Last updated March 5, 2026.