Trump announced the news on Twitter.
"I am pleased to announce that Congressman Mark Meadows will become White House Chief of Staff. I have long known and worked with Mark, and the relationship is a very good one," he wrote.
"I want to thank Acting Chief Mick Mulvaney for having served the Administration so well. He will become the United States Special Envoy for Northern Ireland. Thank you!"
With Mulvaney's new position in the State Department, it's unclear what will become of his role as director of the Office of Management and Budget.
Meadows, R-N.C., announced in December his retirement from Congress at the conclusion of his fourth term later this year.
Meadows said he "struggled" with the decision after eight years representing western North Carolina's 11th Congressional District, but always knew his time in Congress was temporary. There have been previous rumors linking him to multiple jobs in the Trump administration, including the chief of staff post.