NBA player Iman Shumpert was arrested for having a "sizeable" amount of marijuana in his backpack at the Dallas/Fort Worth Airport on Saturday ... TMZ Sports has learned.
According to the police report, officers responded to a potential drug violation call around 2:40 PM ... after TSA screeners found a plastic bag filled with a "green leafy substance" in Shumpert's bag, which he admitted was weed.
Cops say the substance weighed 6.12 ounces and tested positive for marijuana using a mobile test.
The report adds 32-year-old Shumpert -- who was set to board a Delta plane to Los Angeles at 3 PM -- expressed concern about missing his trip to visit his daughter .