Patrick Mahomes rocks a Kansas City Chiefs jersey on Sunday, but he's a Texas native at heart ... and that's why the 3x NFL MVP pulled up with his wife Brittany to cheer on the Dallas Mavericks for the pivotal third game vs. the Boston Celtics in the NBA Finals!
The 3x Super Bowl champ was spotted courtside (where else?!) with Britt at American Airlines Center ... where the couple was all smiles for the cameras.
It's not the first playoff game the Mahomes' have attended .