Middleweight champion Johnny Eblen and Britain's Fabian Edwards had to be separated at a heated face-off before their title bout at Bellator 299.
Tensions threatened to boil over when the pair met after making weight for Saturday's fight in Dublin.
Security intervened as they exchanged words while being spurred on by onlooking team-mates.
Edwards' team repeatedly said "and the new", which was met by chants of "and still" by American Eblen's contingency.
Birmingham's Edwards, 30, is aiming to join his brother and UFC welterweight title holder Leon, as a world champion.
Leon was in attendance to support his younger sibling at the weigh-in, nodding in approval as he walked on stage, but was quiet, disengaging from most of the heckling.
As 31-year-old Eblen was introduced, he raised his belt emphatically towards the audience, before outlining his desire to defeat Edwards and remain champion.
Eblen, who is unbeaten in all 13 of his fights, will be making the second defence of his belt, while Edwards comes into the bout on a three-fight winning streak after beating former champion Gegard Mousasi in a title eliminator in May.
ncG1vNJzZmivp6x7o67CZ5qopV%2BovbC%2B02ikorCVmXqurdGtoJqkXZa%2Ftb%2BOb21xcWJthXo%3D