The singer, 39, told Ellen DeGeneres during an appearance on her talk show, which will air Monday afternoon.
“He’s awesome and so cute. Nobody’s sleeping,” Timberlake gushed in the preview clip. “But we’re thrilled. We’re thrilled and couldn’t be happier. Very grateful.”
DeGeneres said she was one of few close family friends who knew the exciting news.
“I think we were FaceTiming and you said, ‘Hey, you want to know a secret?’ and then Jessica walked in and you put your hand on her stomach. You were like, ‘I’m having another baby!'” she said.
The couple was reportedly able to keep the pregnancy a secret during the pandemic because they spent most of their time in Montana with their firstborn son, Silas, 5.
Timberlake said Silas is “super excited” about becoming an older brother.
“Right now he’s very much liking it,” revealed the actor/producer. “Phin can’t walk yet or chase him down, so we’ll see what happens.”
Back in April 2018, Biel told Entertainment Tonight she was hoping to expand their family.
“Kids are amazing. They are really hard, but they are really amazing,” she said. “I think it would be amazing to have a bigger family. I don’t know if that is in the cards for us, we will see.”
Timberlake and Biel married in 2012.
Timberlake is prepping to perform during a TV special on Wednesday night in honor of President-elect Joe Biden and Vice President-elect Kamala Harris’ inauguration.