T.I.'s entourage was beefing with security at the BET Awards ... and the heated showdown was caught on video.

Check out the footage from before Sunday's award show at the Peacock Theater in Los Angeles ... both sides fire off expletives before one man is shoved back ... and tempers flare as T.I. gets a front-row seat to all the action.

A security guard dares T.I.'s entourage ... "Whatchu wanna do?" before adding ... "I'll f*** your a** up!" He's slowly driven back, away from T.I., as he yaps about a gang affiliation and begs for a fight outside.

The confrontation caused a major scene ... playing out in a backstage area where other groups were posing for photos.

Unclear what sparked this whole showdown ... but, at least based on the video, it looks like cooler heads prevailed.

We reached out to T.I.'s camp ... so far no word back.