Including a photo of herself and Archie from 2017 and a photo of the pair today, the difference in her son was staggering.
“The more things change, the more they stay the same,” she wrote in the caption. “(L) March 2017: Year 7 Mother-Son dinner. (R) Tonight: Year 12 Valedictory dinner.
“I probably didn’t need to point out which was Year 7! Our final school function for Archie.”
The photo on the left shows a much shorter Archie in his uniform, as Kylie stands smiling proudly by his side.
On the right, while Archie is still wearing his school uniform, he now towers over his proud mum.
In a sweet detail, Kylie is wearing a similar black and white outfit in both photos.
The star’s friends and fans were quick to comment on how much the 17-year-old had changed over the years.
“Archie’s grown taller than you. Much muuuuuch taller,” Big Brother's Angela Clancy commented.
“How special! Congrats to your boy,” Miss Universe Australia Maria Thattil added.
“How proud you must feel Kylie, understand completely,” a fan chimed in.
“Oh I love this! Archie!! I still remember him this little, can’t believe it’s gone so fast,” another said.
Kylie’s celebrity pals were also shocked by how the host ‘hadn’t aged’ over the five years.
“Archie aside…you have not aged in that entire time!!” Sunrise star Edwina Bartholomew pointed out.
“Are you Benjamin Button!!?? Completely ageless,” added Seven newsreader Angela Cox.
Kylie praised for 'working mum' comment
This comes after the TV host shared a 'relatable mum' moment.
Posting a video on Instagram, Kylie showed she was live streaming her son's winter schools sports assembly in an ad break so she could see him receive school colours for his AFL.
"Working mums. You just do what you've gotta do, right?" she captioned the video.
"Like watch a school assembly in your work commercial break."
Kylie added it was the first winter sports assembly since 2019 due to the pandemic and said her husband Tony was able to be there in person.
"I'm taking a couple of days off for the final valedictory events in a few weeks," she wrote.
"In the meantime ... how terrific is technology! His grandma watched from Queensland."
A woman who said she was a breakfast news presenter commented on the post, saying it was, "SO SO relatable".
"We need to support other mums like us – in fact ALL mums – who do their best every single day AND their partners," she said.
"Awesome that you could share in Archie's achievement, Kylie," another commented.
"Totally relatable," a third added while a fan said, "Wonderful you could watch and live stream it. Takes away mother guilt".
Never miss a thing. Sign up to Yahoo Lifestyle’s daily newsletter.
Or if you have a story idea, email us at email@example.com.