Philbin was a guest host on CBS' "Late Show" after Letterman underwent heart bypass surgery in 2000. He also stepped in when Letterman was recovering from an eye infection in 2003.
"Very appropriate," said "Live" co-host Kelly Ripa, who made the announcement Monday on the syndicated talk show.
Philbin, 75, has been at home recuperating since his surgery last month.
He has been a frequent guest on Letterman's late-night show.
The Walt Disney Co.'s Buena Vista Television distributes "Live With Regis and Kelly." CBS is a division of CBS Corp.