The couple was first romantically linked in April of this year.
Chalamet and Jenner first sparked a romance in April, when a source told ET the couple was enjoying each other's company.
"They are keeping things casual at this point," the source said at the time. "It's not serious, but Kylie is enjoying hanging out with Timothée and seeing where it goes. It's been really fun for her because it feels a lot different than her past relationships. It's new and exciting for Kylie and she's having a lot of fun."
Neither star has addressed the romance publicly nor have they stepped out together in an official capacity. In May, Jenner, 25, was spotted at 27-year-old Chalamet's home in Beverly Hills. She also attended a family barbecue with her sister, Kendall Jenner, and Timothée's sister, Pauline Chalamet, both on hand.
In June, a source confirmed the pair was still together, but moving slowly.
"They're still taking things slow," the source said. "She's enjoying this time and seeing where things go. She is being mindful of her kids as her main priority is always being a great mom."
Jenner is mom to Stormi, 5, and Aire, 1, both of whom she shares with her ex, Travis Scott.
As for Jenner and the "Sicko Mode" rapper, a source said they are working together to co-parent their children.
"Kylie and Travis are co-parenting well. They’ve both been doing their own things and doing their best to respect one another," another source told ET. "They get along and make their kids a priority. Kylie is a very hands on mom and involved in every way."
The source added about the rapper's current relationship status, "Travis isn’t dating anyone seriously at this point."
For his part, he's focusing on the music. Last month, Scott released a new song, "Meltdown," that some believe to be a reference to Jenner's new love life.
In the song, Scott sings "Chocolate AP and chocolate the Vs got the Willy Wonka factory/ Burn an athlete like it's calories/ find another flame hot as me, b**ch!!!"
AP is short for Audemars Piguet, a luxury watch brand favored by rappers. Fans think that this is a clear reference to Chalamet, who plays the fictional chocolatier in the upcoming film, Wonka.