The 32-year-old reality star shared a photo of herself and the 25-year-old NBA star cozying up in coordinated outfits Sunday on Instagram.
"Him," she captioned the picture, adding a heart emoji.
Kardashian's post follows reports that Thompson welcomed a son with his ex-girlfriend Jordan Craig this month. Craig gave birth via a C-section Dec. 12, according to X17 Online.
"Khloe's really understanding about Tristan's situation -- she's a little embarrassed that her boyfriend is having a baby with someone else, but it happened before she hooked up with Tristan," a source said.
"I love athletes. Someone who has the same interests as me, who likes to work out, like that's their hobby or their job, that's fine. Tristan is who I'm into. He's a little cutie," the star gushed.
The Keeping Up with the Kardashians star finalized her divorce from former NBA player Lamar Odom this month. She initially filed to end their marriage in 2013, but put proceedings on hold following Odom's hospitalization in October 2015.
"[They're] ready to move on with their lives," a source previously told Us Weekly.