CNN/US President Jonathon Klein said Brown was a "first-class news talent" but there was no longer room for him in the evening news lineup.
"It is, unfortunately, a zero-sum game," Klein told the New York Times.
Cooper's show, "360," will be expanded to two hours and moved from its 7 p.m. Eastern timeslot to the 10 p.m. slot held the last four years by Brown's "Newsnight."
CNN has seen a marked increase in viewership at the 10 p.m. hour in recent weeks after Cooper was brought on to share anchoring duties with Brown, the Times said.
Cooper's 7 p.m. time slot will be filled with the final hour of Wolf Blitzer's three-hour long "Situation Room."
"We want to expose Anderson and Wolf to more people," Klein said.
Klein said Cooper's name has been "on the tip of everyone's tongue" for his Hurricane Katrina coverage.