Timberlake said in an interview to air on Monday's edition of The Ellen DeGeneres Show that his infant son's name is Phineas.
DeGeneres shared a preview of the virtual chat on Twitter Sunday night.
"He's awesome and he's so cute," Timberlake said of his baby boy after DeGeneres prodded him for details. "Nobody is sleeping, but we are thrilled."
The couple had not publicly announced they were expecting or had welcomed a child before this confirmation.
The singer did not say exactly when Phineas was born.
Timberlake, 39, and Biel, 38, have been married since 2012. They are also the parents of a 5-year-old son named Silas.