They both announced the news on Saturday (21 February) with a stunning picture of their daughter Pearl cuddling Lisa's baby bump.
In the snap, Lisa looks blissfully happy - and quite pregnant!
While Pearl, who will be three in April, looks the spitting image of daddy in the adorable picture.
Sharing the photo on his official Instagram page, 29-year-old Jack wrote: "Supprise!!!!! #round2 #babyinbound http://raddestmom.com/."
Meanwhile, Lisa posted the picture and a message on her website Raddest Mum.
Lisa, 27, said: "I'm pregnant! Pearl is very happy to become a big sister. She diligently reads her 'I'm a big sister' books every night & recites to me her plans of bathing, feeding, singing to, and holding the baby.
"We are more than halfway through this thing & are very excited to be parents again! Thanks for all the well wishes."
The news is bittersweet after Lisa suffered a late term miscarriage in 2013.
They announced they were expecting again in August 2013 but, two months later, revealed Lisa had tragically lost their baby boy in her second trimester of pregnancy.
In 2012, Jack was diagnosed with Multiple Sclerosis and has campaigned to raise awareness ever since.
A huge congratulations to Jack and Lisa on their happy news!
What do you think of Jack and Lisa Osbourne's good news? Tell us in the comment box below and you could win £50!
For exclusive competitions and amazing prizes visit Reveal's Facebook page NOW!