Cleveland Cavaliers player Tristan, 27, was spotted snogging and cavorting with Kylie Jenner's best friend Jordyn Woods around Valentine's Day in LA.
When news broke of the snog Us Weekly claims Khloe confronted baby daddy Tristan who confirmed it's true.
A source said: "Khloe was told by people who saw Tristan and Jordan making out and told Khloe, and Khloe confronted Tristan and he admitted it was true.
Adding: "Khloé is completely done with him for good."
After refusing to initially believe the rumours, the Kardashian family is now "beyond angry and disgusted" with Jordyn, who has yet to comment on the allegations.
Tristan admitted cheating on Khloe back in April last year - but she stayed with the love rat after giving birth to baby True.
It comes after Khloe and Kim Kardashian appear to have confirmed reports that Tristan cheated with Jordyn Woods.