O'Brien left NBC after the network attempted to bump "The Tonight Show with Conan O'Brien" from 11:35 p.m. to 12:05 a.m. to make room for Jay Leno's show earlier in the evening.
O'Brien's "Tonight" was on for only several months in the 2009-10 television season before Leno returned as host.
"Thank you and welcome to my second annual first show," O'Brien told the "Conan" audience Monday night.
"Yes, I know what you guys are thinking, 'Hey, it's the guy from Twitter,'" he quipped. "Welcome to my new show, 'Conan.' People ask me why I named the show 'Conan.' I did it so I'd be harder to replace. This is an exciting night. I'm glad to be on cable. The truth is, I've dreamed of being a talk show host on basic cable ever since I was 46. And things are going well already. I'm happy to report that we're already No. 1 in TBS's key demographic -- people who can't afford HBO. I'm going to be honest: It's not easy doing a late-night show on a channel without a lot of money and that viewers have trouble finding. So that's why I left NBC."
O'Brien also noted a lot has happened in the news while he was in between TV gigs.
"And I was hoping I could cover it all in one joke," he said. "But then I realized that's like trying to keep an Icelandic volcano from wearing Lady Gaga's meat dress while a trapped Chilean miner cleans up the BP oil spill."