The proud new mum posted an adorable photo of the new arrival on her Twitter account, alongside the caption: "Here's my gorgeous Harry x."
Jennifer, who also has a three-year-old called Bobby, gave birth to her son six weeks ago, but has waited until now to share a glimpse of the little one.
She has been keeping a low profile since the complicated birth, when she had to stay in hospital for five days after doctors suspected she had a blood clot.
Jennifer, 30, didn't get the chance to make the grand announcement of her new arrival to the world on 9 July.
Instead it was her good friend Danielle O'Hara, who pipped her to the post with a tweet: "Congratulations to my lovely friend @Jelliofficial on the birth of Harry Tickle such a cute name can't wait to meet him well done babe."
A few hours later, new mum Jennifer took to Twitter: "Thank you so much for all ur lovely messages!! On cloud 9!! Baby Harry is absolutely gorgeous!!!"
Two days later, she tweeted: "Thanks for all ur messages! Still in hospital, but on the mend! Being well looked after and got the best present in the world!"
The following day, upon learning that she had to stay in hospital a while longer, the actress wrote: "Don't look like I'm going anywhere fast!! ;( x"
She was also readmitted to hospital after being discharged after developing an infection in her womb. "Back in hospital!! ;(" wrote the mum-of-two.
Jennifer has previously spoken about her traumatic 92-hour labour with her first child Bobby in February 2010, which resulted in an emergency Caesarean section.
After Bobby's birth, she ended up suffering from post-natal depression, but she seems to be keeping her spirits up this time around.
"In hospital for the hottest day of the year!!!", wrote the mum when she was still in hospital. "Snuggling my baby though so don't care!!! X"