Months after merging with Viacom, CBS announced a significant change in its leadership on Friday.

Joe Ianniello, a 22-year veteran of the network who was promoted last year to chairman and chief executive officer, will leave the company. His successor will be George Cheeks, a Viacom alumnus whose most recent post was vice president of NBCUniversal content studios.

Mr. Ianniello managed to stick it out at the upper echelons of CBS through times of success and turmoil. For years he was the No. 2 under Leslie Moonves, the longtime chief executive who was ousted in 2018 after several women accused him of sexual assault, allegations he has denied.

Mr. Ianniello became the acting chief executive after Mr. Moonves’s departure. When a job search failed to turn up an option to the liking of the company’s controlling shareholder, Shari Redstone, Mr. Ianniello’s term was extended ahead of the planned merger with Viacom.

After the merger deal closed, Mr. Ianniello received a $69 million payout thanks to a provision in his contract that granted him a significant sum if he was not named chief executive of the newly combined company. That title went to Bob Bakish, a longtime Viacom executive and a close confidant of Ms. Redstone.