CNN did not immediately say what Brown would be doing. There has been widespread speculation about a prime-time shake-up at CNN, where Paula Zahn has been lagging in the ratings at 8 p.m. ET.
Brown, 39, had been co-host with Lester Holt of "Weekend Today" since 2003 as well as correspondent and occasional fill-in anchor on NBC's "Nightly News." She's a former White House reporter who also covered the 2000 presidential election for NBC News.
Brown was considered a potential successor to Katie Couric for the weekday "Today" post, a job that went to Meredith Vieira.
"We wish Campbell the best," said Allison Gollust, NBC News spokeswoman. "We'll have an announcement on her replacement in the coming months."
Several different anchors will be filling in over that time, she said.