The U.S. Senate voted to confirm Markwayne Mullin as secretary of homeland security on March 23, 2026. The Senate voted 54-45 in favor of his nomination, with 52 Republicans and two Democrats, Sens. John Fetterman (D-Pa.) and Martin Heinrich (D-N.M.), voting in favor. Forty-two Democrats voted against the nomination, along with two independents who caucus with Democrats, and one Republican, Sen. Rand Paul (R-Ky.).

Trump announced on March 5, 2026, that he was removing Kristi Noem from the position and nominating Mullin to succeed her. Trump said of Mullin’s nomination, "Serving 10 years in the United States House of Representatives, and 3 in the Senate, Markwayne has done a tremendous job representing the wonderful People of Oklahoma... Markwayne will work tirelessly to Keep our Border Secure, Stop Migrant Crime, Murderers, and other Criminals from illegally entering our Country, End the Scourge of Illegal Drugs and, MAKE AMERICA SAFE AGAIN." The Senate Committee on Homeland Security and Governmental Affairs held a confirmation hearing for Mullin on March 18, 2026, and voted 8-7 to advance his nomination, with one Democrat, John Fetterman (D-Pa.), voting to advance his nomination and one Republican, Sen. Rand Paul (R-Ky.), opposing it.

Mullin earned an associate degree in construction technology from Oklahoma State University Institute of Technology. He has owned and operated various small businesses, including his family’s plumbing business. Mullin served in the United States House of Representatives for Oklahoma’s 2nd Congressional District from 2013 to 2023, and in the United States Senate from 2023 to 2026.

A presidential Cabinet is a group of senior federal officials who advise the president on the issues and activities of their respective agencies. The number of officials in a Cabinet can vary across presidential administrations. While not explicitly identified in the Constitution, the Cabinet secretaries are the 15 agency heads who are in the presidential line of succession. The vice president is also part of the Cabinet.

During Trump's second term, the following offices are also Cabinet-rank positions: White House chief of staff, the administrator of the Environmental Protection Agency, the director of the Office of Management and Budget, the U.S. trade representative, the director of the Central Intelligence Agency, the director of National Intelligence, the administrator of the Small Business Administration, and the ambassador to the United Nations.