Expected to debut in November, the as-yet-untitled show will return O'Brien to the air after an absence that began in January when he left NBC, his employer of 17 years.
O'Brien's new program will air Mondays through Thursdays at 11 p.m. Eastern, which will shift "Lopez Tonight," starring George Lopez, to midnight. O'Brien's show will originate from Los Angeles, where he moved from New York for his unsuccessful stint hosting "The Tonight Show." And the second half of his show will face off against Jay Leno, who now hosts "Tonight."
Upon TBS' announcement Monday, O'Brien quickly fired out a celebratory tweet.
"The good news: I will be doing a show on TBS starting in November! The bad news: I'll be playing Rudy on the all new Cosby Show," he posted on Twitter.
TBS said that talks with O'Brien accelerated last week after Lopez called O'Brien to ask him to come aboard.
"I can't think of anything better than doing my show with Conan as my lead-in. It's the beginning of a new era in late-night comedy," Lopez said in a statement released by TBS.
There's a seemingly ironic ring to the time change for Lopez, who became the first Latino to host a nighttime talk show on a major network when his TBS show debuted last fall. O'Brien rejected NBC's effort to move him to a later slot to make way for Leno. This dispute led to O'Brien's abrupt exit.
"Until George Lopez called Conan last Wednesday, Conan would not have even considered a deal at TBS that would have uprooted Lopez," said a person close to the talks who spoke on condition of anonymity because the person wasn't authorized to discuss that part of the negotiations. The deal was signed on Friday, the person said.
O'Brien left NBC in January after hosting "The Tonight Show" for just eight months, as his ratings plunged from those of his longtime "Tonight" predecessor, Leno, who then reclaimed the hour. Until last June, O'Brien had followed Leno as host of "Late Night" since 1993.
After giving O'Brien "Tonight," NBC sought to keep Leno on board with a prime-time show that quickly flopped. An attempt to move O'Brien to a post-midnight slot drew O'Brien's ire, and he walked away with a $32 million settlement package.
Although that put him in play for other networks, the deal barred him from appearing on TV until September.
Monday's surprise announcement hit only hours before O'Brien was to start a two-month, nationwide comedy tour in Eugene, Ore., aptly titled "The Legally Prohibited From Being Funny on Television Tour."
The news laid to rest persistent reports that he was likely to land at the Fox network.
"Conan is a great talent and we wish him every success," Fox said in a statement.
Fox told O'Brien's representatives last week that the network would not be making a deal with him, said an executive with knowledge of the talks who spoke on condition of anonymity because the person was not authorized to discuss negotiations.
The network realized it would not be able to clear airtime for O'Brien in a manner that made sense. Most affiliates have contracts for syndicated shows airing in late-night hours that expire at different times. The idea of an O'Brien show premiering at different times over a two-year period seemed unwieldy, the executive said.
Fox network management had pushed to make it happen, realizing O'Brien represented perhaps their best opportunity to launch a late-night talk show, given his popularity with the type of young audience Fox seeks.
But some of the affiliates had also questioned whether a network talk show would prove as lucrative for them as selling their commercial time for shows they aired themselves.
Barring Fox, syndication to individual stations was widely considered O'Brien's most likely option.
All the while, few if any handicappers cited TBS as a plausible destination.
But adding O'Brien to its lineup makes sense for TBS, which, available in 100.4 million of the nation's 114.9 million TV homes, has branded itself as the place of comedy with its slogan, "Very Funny."
Conan's show is "an extension of that strategy," said Christopher Marangi, a media company analyst for Gabelli & Co.
The effect on other late night shows was unclear, but no doubt O'Brien would draw viewers, Marangi said. "Conan has a fan base and probably a good number of fans will follow him to TBS."
But the second half of O'Brien's show will meet fierce talk-show competition from broadcast networks: CBS' "Late Show With David Letterman" and, on NBC's "The Tonight Show With Jay Leno," the host who, by one interpretation, vanquished O'Brien.
On cable, he'll face off against Comedy Central, whose pair of marquee comedy half-hours "The Daily Show With Jon Stewart" and "The Colbert Report With Stephen Colbert" also begin at 11 p.m.
Comedy Central had no comment on O'Brien as an imminent rival.
Ben Silverman, the former NBC entertainment chief, said O'Brien's move to cable from a broadcast network further blurred distinctions about where people watch their shows.
"I think what it means is everything is open for discussion," he said. "I wouldn't have been surprised if we were talking about it being on YouTube. I think the walls are breaking down."
TBS is owned by Time Warner Inc.