The long-running program, currently airing on NBC, will run in primetime on ION Television.
ER has won 22 Emmy Awards over the course of its run.
“This deal with Warner Bros. highlights ION Television’s evolution both in terms of programming and target audience -- a major consideration for advertisers,” said ION chairman and CEO Brandon Burgess, a former NBC executive. “ER is one of America’s most acclaimed series. The addition of this show underscores our network’s commitment to contemporary, quality programming that will appeal to a wide audience.”