Jim Acosta, a CNN anchor who earned notice for grilling Trump administration officials in the White House Briefing Room, said Tuesday that he was leaving the network after nearly 20 years.

Mr. Acosta announced the decision at the end of his 10 a.m. show, which will be his last for CNN. He is stepping down after clashing with the network over a decision to move his show to start at the midnight hour, a cable news backwater, according to two people with knowledge of the discussions.

The network is moving Wolf Blitzer, a well-known CNN anchor, into his time slot, along with a co-anchor, Pamela Brown. Mr. Acosta’s show is third place in his time slot for total viewers, behind both MSNBC and Fox News, though he has outperformed his MSNBC competitor in the key demographic for advertisers.

In a statement, CNN said it was grateful for Mr. Acosta’s track record of “dedication and commitment.”

“Jim has had a long, distinguished nearly 20-year career at CNN, with a track record of standing up to authority, for the First Amendment and for our journalistic freedoms,” the statement said.

Mark Thompson, CNN’s chief executive, informed Mr. Acosta this month that the network wanted to move him to midnight as part of a reorganization of the network’s lineup, the two people said. Mr. Acosta was resistant to the idea, wary that he was being shuffled to the graveyard shift as part of a plan to sideline journalists who have been critical of President Trump.

Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.

Thank you for your patience while we verify access.

Already a subscriber? Log in.

Want all of The Times? Subscribe.