The veteran TV personality made the announcement on Tuesday's edition of "Live with Regis and Kelly" as it began its 24th season in national syndication.
Philbin announced last January that he planned to leave the show by year's end, but didn't specify a date. The show will continue with Kelly Ripa, who joined him as co-host a decade ago.
No new co-host has yet been chosen to team up with Ripa.
Philbin, who turned 80 last month, has been a TV fixture since the 1950s. A three-time Emmy Award winner, he was honored with a Lifetime Achievement Award from the National Academy of Television Arts & Sciences at the Daytime Emmy Awards in 2008.