Each fighter tipped the scale at 145 pounds.
During the staredown, Poirier was in no mood for pleasantries. While Jung offered a slight smile, Poirier remained tightlipped and refused to shake hands when UFC matchmaker Joe Silva tapped each on the shoulder to signal they could separate.
Poirier (12-1) is ranked third among featherweights by ESPN.com. He enters the bout on a five-fight win streak. Jung, who is ranked No. 9, has a professional record of 12-3.
Every other fighter on the UFC on FUEL 3 card qualified to compete Tuesday night at Patriot Center. The event will consist of 12 bouts.
Welterweights Amir Sadollah and Jorge Lopez made use of the extra pound they were allotted for their nontitle co-feature bout, checking in at 171 pounds.