Jamie announced the incredible news on Instagram, penning this heartfelt post:
"And then this just happened guys !! IT'S A BABY BOY !!"
Alongside a darling photo of his newborn, the proud daddy continued, "Everyone in the Oliver family is very surprised and beyond happy."
"He arrived safely, mum / @joolsoliver was really really amazing, unbelievably composed, natural birth and my two eldest Girls got to come in at the very end as the baby was born which was amazing to witness very very emotional.
"8 lbs ( that's 16 packs of butter for you bakers out there) anyway were all hitting the hay it's been a long day big love... bless a little baby boy Woop Woop !!!!"
Before sending one more shout-out, "And love to all you mums out there how amazing you are it blows my mind.... Big love jamie o p.s no baby names yet."
Jools also shared the incredible moment on Instagram, signifying the birth with a breastfeeding snap.
"Little baby boy Oliver has arrived we are so very happy, blessed, grateful and totally in love all over again and so very proud of our two eldest daughters who cut the cord ❤️ "
"Jamie was my hero (no name yet)!!! XXXX," she concluded.
Check out Jamie after the birth of his first son, Buddy! The proud dad can't stop smiling! Post continues...
The 41-year-old mother debuted her prominent baby bump back in March at the European Premiere of Eddie The Eagle at Odeon Leicester Square.
Speaking at the event to The Mirror, Jamie couldn't help but gush about his wife, "I thought we'd have a couple of kids but that's about it. Basically I do what I'm told but she's an amazing family maker and I just go with it!"
"I love kids. My family keep me honest, I have a weird job, a weird life, but my family keep me quite real."
When asked whether he wanted a boy or girl, the proud dad simply quipped, "You know what, I'm always grateful for what I get, it would be nice to balance it out a bit."
The couple are already parents to Poppy Honey Rosie, 14, Daisy Boo Pamela, 12, Petal Blossom Rainbow, six, and their youngest son, five-year-old Buddy Bear Maurice.
In 2010, following the birth of their youngest, Jamie revealed how is wife loves naming her kids with unusual names.
“That would be my wife,” he told Sharon Osbourne of their quirky monikers.
“Jools is definitely in charge of the names, and we’re probably quite lucky it was a boy really, because we were out of names [for] girls.”
It's no secret that Jools wanted more kids. In 2012, she told Red magazine: "I want a fifth," she said.
"But I know it would be wrong. I never get any time to spend with Jamie as it is. He has said give it a couple of years, then maybe we can think about it."
Congratulations to the Oliver family!