The 'Justified' singer FINALLY confirmed the good news on Saturday night (31 January) - which just happened to be his 34rd birthday, too.
This follows months of speculation about Jessica's usually flat stomach getting rounder and rounder!
Justin announced the fantastic news to his Twitter and Instagram followers by sharing an adorable photo of himself kissing wife Jessica's baby bump - awwwwww.
And, by the looks of her swollen tum, we think she must be in her third trimester!
He wrote: "Thank you EVERYONE for the Bday wishes! This year, I'm getting the GREATEST GIFT EVER. CAN'T WAIT. #BoyOrGirl #YouNeverKnow #WeDontEvenKnow #WeAreTakingBets."
Thank you EVERYONE for the Bday wishes! This year, I'm getting the GREATEST GIFT EVER. CAN'T WAIT.… http://t.co/Kr2s9U0Jlp— Justin Timberlake (@jtimberlake) January 31, 2015
Thrilled fans were quick to express their delight at the fabulous news.
One said: "Honestly the cutest thing to ever happen."
While another gushed: "You are going to be the coolest dad ever."
One fan spoke for all of us, when they wrote: "Awww gorgeous! Beautiful mamma x."
The popular showbiz couple have been together since early 2007, and became engaged four years later.
They tied the knot in Fasano, Italy, at the exclusive Borgo Egnazia resort in October 2012.
A huge congratulations to one of our favourite celebrity couples!
What do you think of this news? Tell us in the comment box below and you could win £50!
Reveal is now on Google Plus! Join us here for the latest pictures, fashion and celebrity news!