"I feel a little intimidated by him, too," she joked after host Jimmy Fallon commented on how the toddler wears the "coolest" clothes. "It's kind of like a mini Justin. It's his style. He's got, like, a daddy swagger."
Biel and Fallon, who shares daughters Winnie and Franny with wife Nancy Juvonen, got together with their families over Memorial Day weekend. Fallon said Biel saved the day by bringing snacks on the group's bike ride.
"That is mom style," the actress explained. "I do not leave the house -- I don't care if it's a bike, a scooter or one of the 400 cool toys you have at your house, which I'm dying to own myself -- I'm going to have pretzels, veggie sticks, apples, string cheese. I'm going to have supplies."
"You always have snacks if you're rolling with me, I promise," she vowed.
Biel and Timberlake married in Fasano, Italy, in 2012, and welcomed Silas in April 2015. The actress said in the August issue of Marie Claire that the secret behind her happy marriage to Timberlake is their similar beliefs and interests.
"We have similar values; we believe in honestly, loyalty," Biel told the magazine. "We like to have fun. We like a lot of the same things."
"Also, in the business, we're all very career-oriented, and you have to be a little selfish," she added. "I understand that about my peers -- about being focused and driven -- and if you can find that and someone who shares the same values as you, it's like: Score!"
Biel will next star on the USA Network series The Sinner, which premieres Aug. 2.