The 34-year-old actress, who plays Fiz on Coronation Street, broke the news to fans – revealing she is due later this year.
She tweeted: “We’ve got a bit of news. Pur baby boy is going to be a big brother later this year. We can’t wait to meet you precious one x” (sic).
The star is already mum to a son called Albert with her husband Chris Farr.
Following her announcement she was inundated with messages of congratulations from fans and her celeb pals.
We’ve got a bit of news. Pur baby boy is going to be a big brother later this year. We can’t wait to meet you precious one x— Jennie McAlpine (@jenniemcalpine) April 15, 2018
Sherrie Hewson told her: “Congratulations gorgeous xxxxx.”
While Samia Longchambon tweeted: “Oh wow Jen! Fabulous news... congrats to you all darling! ❤❤❤??? xxx”
And Shobna Gulati added: “Congratulations my dearest ! To all of you !! (especially you as you are brewing baby).”
Jennie tied the knot with husband Chris in 2017, after they started dating back in 2005.
The couple married in secret and revealed the news online with a picture of their wedding bands.
"So, we went to Trafford Town Hall earlier this week and had a bit of a special day," she told fans.
She gave birth to son Albert on 29th November 2014 and was devastated when she missed his third birthday last year during her stint on I'm A Celebrity.
She told the Daily Star at the time: "It was emotional saying goodbye to him.
"So I've already cried before I've got to the jungle. I found it much more difficult than he did.
"I told him: 'Mummy's going to work for a bit and you're staying here. I was trying not to cry. He said to me: 'OK mummy...bye'"."