The 27-year-old singer-turned-farmer shared the exciting news with fans on Instagram and Twitter on May 31.
First he tweeted the message:
"The word of the day today should be ANTICIPATE: to expect; look forward to; be sure of x"
Followed by:
He then uploaded a photo of him kissing Chloe's baby bump to his Instagram account.
It wasn't long before messages of congratulations started flooding in from the couple's famous friends.
JB's former bandmate Aston Merrygold had the fastest Twitter fingers, promptly replying:
Followed by Ortis, who wrote:
"Massive congrats to my boy @JB Gill & @ChloeSGill !!!#BubbaGILLOnTheWayYaaayyyyyy xxxxxxxXXXXxxxxxxx"
Katie Piper also got in on the action, tweeting: "awwwwww! This has just put a huge smile on my face! Congrats both of you :) x"
As did Marvin Humes and his wife, The Saturdays singer Rochelle, who tweeted:
Marvin and Rochelle welcomed their first baby, Alaia Mai, in May 2013, so JB and Chloe will no doubt be turning to them for advice about what to expect in the coming months.
JB and Chloe married in Scotland in May after meeting on the set of the X Factor five years ago. Chloe, who has danced for artists such as Beyoncé and Jessie J, was working as a backing dancer during the fifth series of the show, when JLS finished second to Alexandra Burke.
Following JLS's split in April 2013, JB started running a working farm. Speaking about his career change to Hello! magazine he said:
"Farming is something I care about deeply. I never wanted to be a 'gentleman farmer' and have someone else running everything."
At the time he also hinted that he and Chloe were likely to start trying for a baby soon after they were married.
"We get asked about marriage and babies all the time," he said. "For me, it would be marriage then babies. I'm definitely traditional in that way. But it's definitely something that I would like to focus on."