As Biel turned 38 on Tuesday, Timberlake, 39, took to Instagram to share several pictures of the two of them cuddled up.
"Happy Birthday to the LOVE of my life... A new adventure every day and a treasure to me," he wrote in the caption. "I can’t wait to share many more of these with you. Thanks for putting up with me when I smell funky after a round of golf or, when I smell funky in general. You are the mostest of the mostest, my love! I adore you."
Timberlake signed the post: "HUZ."
Biel quickly commented, writing, "As you always say, you can’t be funky if you don’t smell funky."
The post contained four photos of the duo, one being from a Halloween party when Biel dressed as Timberlake, and he went as a microphone.
Biel also made an Instagram post earlier on Tuesday, sharing photos from a recent evening spent with her hubby.
In the pics, Biel, dressed in pajamas, sits at a table with Timberlake serves her cake and hugs her.
"Celebrating my birthday in style... and by that I mean, in pajamas," the caption read. "I made Justin PROMISE not to sing Happy Birthday to me, so he improvised. Sorry you can’t hear it, but I’m still laughing."
She added: "Thank you, you wonderful human, for really listening to me, and for throwing my kinda party. And thank YOU ALL for the birthday wishes. Feeling the love."
Timberlake was the subject of controversy last year when he was seen holding hands with his co-star from an upcoming movie. The singer issued a public apology on Instagram in December, vowing to be "the best husband and father" he can.