"I was his favorite and he was my favorite and I couldn't get over it because he was a phenomenal artist, a beautiful singer and a great person," the legendary performer explained to host Jimmy Fallon after he was shown a picture of the pair enjoying hot dogs together in Miami.
Bennett then shared how Sinatra calmed his nerves before a big performance at New York's Paramount Theater with some words of encouragement.
"He taught me that the audience are your friends," Bennett said of the advice. "They come to see you. [Sinatra] changed my whole psychology about it."
The 90-year-old icon also discussed NBC's Tuesday special in honor of his 90th birthday. The lineup includes some of the biggest names in music including Billy Joel, Bob Dylan, Lady Gaga, Elton John, Paul McCartney, Aretha Franklin, Andrea Bocelli and more.
Alec Baldwin, known for impersonating Bennett, will be hosting the show in character when it airs Tuesday at 9 p.m. ET.
When Fallon asked about Baldwin's impersonation, Bennett replied, "It's pretty good."