Ex-NBA star Sebastian Telfair has been sentenced to 3 1/2 years behind bars for possessing an illegal firearm in 2017 ... TMZ Sports has learned.
As we previously reported ... the 34-year-old former high school phenom was busted back in June 2017 in Brooklyn .... after cops found an arsenal of weapons in his car during a traffic stop.
Officials say the former Trail Blazer, Celtic, Clipper and Timberwolf (to name a few) had 3 pistols and what appeared to be a semi-automatic rifle.
Telfair was convicted of one count of second-degree criminal possession of a weapon back in April ... and was facing up to 15 years behind bars, so it could've been worse for the hooper.
Telfair -- who appeared before the judge -- was taken away by authorities.