"I F**KING LOVE YOU! 🖤YOU’RE A BLESSING TO THIS WORLD HAPPY BIRTHDAY @kourtneykardash," Barker captioned the series of pics and clips of the couple getting extremely close.
In one pic, Kardashian sat on the 45-year-old's lap as they shared a kiss. One picture showed them hugging by a fire pit, and they held hands in another. The final post on the Instagram gallery was a video of the Poosh founder sucking his thumb and laughing.
Famous friends, family and fans took to the comments to gush over the power couple.
"Wow y’all are so hot it’s stupid 🔥," Demi Lovato wrote.
"👏👏👏👏," Barker's daughter, Alabama, left.
Barker reportedly went all out for Kardashian's birthday and treated her to a bowl of gelato and sent a huge display of tulips and gardenias to her foyer over the weekend.
Earlier this month, he was spotted out and about with what looks like Kardashian's name tattooed on his chest.
The pair went Instagram official on Valentine's Day after romance rumors began to circulate in January when they were spotted in Palm Springs together.
"Travis has been in the Kardashians' inner circle for many years now, and he's always had a soft spot for Kourtney — and vice versa," an insider previously told OK!.
"It never felt right for them to date or hook up until now, mainly because they were scared it might mess up their friendship," the source explained about what took them so long to get together. "But the chemistry has always been there. And finally, they've decided to give this a go, have as much fun as possible and see where it takes them."
Now Barker has even reportedly moved some of his stuff to Kardashian's pad, which is in the same neighborhood. "Everyone's convinced they'll be living together full-time before you know it!" an OK! insider predicted.
Meanwhile, all the love Barker leaves on Kardashian's pics is said to be a huge confidence boost for the Keeping up with the Kardashians star. "She's got a real swagger in her step these days — and she's earned it!" a source said.