Many of Carrie's famous friends offered up their own birthday messages to Ollie in the comments section.
TV personality Fifi Box, who is close friends with Carrie wrote: "Happy birthday Ollie I can’t believe you’re 13!! You are the kindest and most beautiful boy with the biggest heart! We love you."
Meanwhile, Dancing With The Stars host Amanda Keller commented: "Just gorgeous. Happy birthday Ollie x"
Carrie's Project co-host Peter Helliar also penned: "Happy Birthday Ollie!! You are such a lovely, kind, compassionate, funny young man."
Budding chef Carrie also shared a snap of Ollie's extravagant birthday cake decorated with an assortment of doughnuts.
"Another fun family lockdown birthday. Ollie turns 13," she wrote in the caption.
Carrie, who shares Ollie with her late husband Greg Lange, established her Beanies for Brain Cancer campaign after losing Greg to brain cancer in 2010.
"One of the things we chose to do was have our son Ollie. I think it's probably the greatest thing we ever did together. He's a gorgeous boy and he's so much like him in so many ways," the TV and radio personality said on Anh's Brush With Fame in 2018.
It appears that Ollie is very proud of his mum's work to keep his dad's memory alive.
"For him, I am very aware that I want him to grow up to be a happy boy and I don't want him to feel a burden of anything," Carrie told TV WEEK.
"But he is so connected to it because it was his dad. He can do a simple thing and put a beanie on and feels that connection. And he wears it so proudly. It's a really lovely thing."
Along with eldest son Ollie, Carrie also shares daughters Evie, five, and Adelaide, one, with current partner, Chris Walker.
"I never thought that I would necessarily have any more kids. I had a really, really traumatic birth with Ollie so I had a huge fear about birth," Carrie confessed.
"I think I thought I would be OK if I didn't have any more kids. I just felt so blessed with Ollie and with Evie, it was a really different experience. It wasn't fun but it wasn't traumatic. I'm so glad I had her!" she added of her youngest daughter.