The 20-year-old television personality rented out Six Flags Magic Mountain amusement park Saturday in Valencia, Calif., ahead of Scott's official birthday Monday, April 30.
E! News said Scott's party paid tribute to Astroworld, a theme park in Houston, Texas, that closed in 2005. Scott was born in Houston, and grew up in nearby Missouri City, Texas.
Jenner shared several photos and videos on social media, including a picture of herself and Scott on a rollercoaster. The couple wore matching custom hoodies with Scott's birthday and place of birth printed on the back.
Jenner's sisters Kourtney Kardashian and Kim Kardashian attended the celebration, along with Kim's husband, rapper Kanye West. West posted a snapshot of Scott's birthday cake, which depicted Scott, Jenner and their daughter, Stormi, on a rollercoaster.
"Happy birthday Trav," West captioned the photo on Twitter.
Jenner and Scott were first linked in April 2017 following Jenner's split from Tyga. The television personality gave birth to Stormi on Feb. 1, and called her daughter her "BFF," or Best Friend Forever, in a new post this month.
"Stormi has brought out a much softer side to Kylie," a source told Us Weekly in March. "She's a very hands-on mom."