Timberlake and Biel have been married since October 2012. In January, the couple announced they were pregnant with their first child.
"Thank you EVERYONE for the Bday wishes! This year, I'm getting the GREATEST GIFT EVER. CAN'T WAIT," he wrote on Instagram, where he posted a picture of himself kissing her belly.
Justin Timberlake Tells Jessica Biel 'I Can't Wait to See Our Greatest Creation'
Timberlake recently accepted the iHeartRadio Innovator Award in Las Vegas, where he made a special shout-out to Biel.
"I want to thank my best friend, my favorite collaborator, my wife Jessica at home," the singer said. "Honey, I can't wait to see our greatest creation yet. Don't worry, daddy's heading home right now to innovate by learning how to change a poopy diaper and get my swaddle on."