Carmelo Anthony -- My Kid's Modeling for Sean John!

As if dominating youth league basketball was't enough, now Carmelo Anthony's kid has also locked up a modeling gig with Diddy's fashion line!!

8-year-old Kiyan Anthony just finished up a photo shoot with Sean Jean -- rockin' some back to school gear along with a designer basketball.

Kid's doing pretty well for himself so far ... as we previously reported, Kiyan's 2nd grade basketball team just dominated in a highly competitive 3rd grade national tournament.

So, how does his mom Lala feel about the situation? Proud.