The pop star and actor loves the spooky holiday and he and Biel have made it a habit to hit the streets dressed in elaborate family costumes, but this year he won't be at home to go trick-or-treating.
"We win Halloween every year, let's be honest," he tells Billboard, "but I'm starting a film very soon and so, unfortunately, it's the first year that we're going to be away from each other for Halloween."
"This is the first year that he (Silas) and mom will be doing Halloween, and I'll be on location."
In previous years, Timberlake, Biel and their son have hit the streets as characters from "The Lego Batman Movie" and Buzz Lightyear, Jessie and Woody from Toy Story - and Justin can't wait to see what his son comes up with this year.
"My son gets to pick our Halloween costumes every year," he says. "He gets to choose, so everything we've ever worn is his choice. As the years go by, that may have to be modified, because you never know what a child will choose!"
"He hasn't chosen yet (this year)... but I will say this. If I had to guess, which I'll probably be way off, he loves Batman. He was Lego Batman last year. So listen, I wouldn't be surprised if he chose that again!"