NBA's Jeff Adrien: Pleads Not Guilty ... I Didn't Jack That Car

Ex-NBA player Jeff Adrien is insisting he did NOT steal a car from a Hollywood hotel valet ... pleading not guilty in court moments ago.

TMZ Sports broke the story... the former UConn star was arrested earlier this month after allegedly jacking a 2015 Mercedes from a parking attendant and taking it on a 6 hour joyride around Los Angeles.

We spoke to Adrien ... and he told us it was all a big misunderstanding ... saying he was trying to borrow a friend's car and got into the wrong one by mistake.

29-year-old Adrien was charged with one count of driving or taking a vehicle without consent. If convicted, he faces up to 3 years in county jail.