Letterman's girlfriend, Regina Lasko, delivered a baby boy late Monday night. He weighed in at 9 pounds, 11 ounces and is 21 inches long, Letterman announced on his show Tuesday night.
"I could never imagine ever being a part of something that turned out this beautiful," Letterman said, according to a transcript from "Late Show," which is taped earlier in the day.
Letterman, 56, said the baby — his first child — is named after his father, Harry Joseph Letterman, who died at 57.
"So God bless dad and God bless Harry," Letterman said.
The talk show host joked: "I don't know, maybe I shouldn't have done this. First thing I took him home and dangled him over the balcony," a reference to pop star Michael Jackson briefly dangling one of his children over a balcony.
Bandleader Paul Shaffer had filled in for Letterman as host of the "Late Show" Monday night when Lasko went into labor. Tom Keaney, spokesman for Letterman's production company, Worldwide Pants, said he didn't know where the baby was born.
The show Tuesday night included a Top Ten list of reason's why Letterman was excited to be a father. The No. 1 reason: There is now tangible evidence that I have had sex.