Border patrol agents say the 18-year-old, along with a 21-year-old passenger, claimed they had nothing to declare when trying to drive into the U.S.
It turns out there was something wrong with the teen's vehicle ID number, so he had to go through another round of inspections.
That's when authorities discovered the endangered Bengal tiger cub inside of the car.
The teen was arrested and the cub is now recovering at the San Diego Zoo.