The 35-year-old actress said Tuesday at the Tribeca Film Festival premiere of The Sinner that Timberlake has done nothing but support her "dark" role in the new USA Network series.
"He supported me from the very beginning," Biel told E! News. "He's excited because I'm excited. He's just been a wonderful partner. Completely supportive, even though it is dark."
"I have to really put myself out there in a way that feels a little scary and is a little exposing," she said of the show. "He understands because he's an actor and that's what we do. He's just been a great partner in all of it."
Biel plays Cora Tannetti, a young mother who shocks with a public act of violence, on The Sinner. The series is based on the Petra Hammesfahr novel of the same name, and explores why Cora committed the seemingly random and senseless crime.
"I just wanted to play that girl and get to be a little nuts," Biel said at a post-premiere Q&A, according to Indie Wire. "Obviously, she's a terribly complex and complicated person ... Through the series, we're going to slowly peel the onion of her and her mind and her past and everything."
"The tracking of what she knows, what she remembers, what she thinks she remembers, what is a lie, what was told to her, and when she's lying, it's very complicated," she added. "There's all this weaving of this denial and this shame and all these things, and this truth that she really does believe."