KSI shoved Tommy Fury in an intense face-off where the pair nearly came to blows.
The two fighters took part in a stacked press conference at the Wembley Arena ahead of their fight on October 14 in Manchester.
KSI was joined by his business partner Logan Paul, who is squaring off against MMA fighter Dillon Danis on the same card.
Advert
Insults were traded and tempers flared and it all kicked off completely when Tommy's dad John lost his head and started smashing up the set.
The 59-year-old grew tired of the jibes and antics from fighters much younger than him and KSI's comment where accused his WBC world heavyweight champion son Tyson Fury of ducking Oleksandr Usyk proved to be the final straw.
Fury Sr flipped tables and security had to intervene, with the press conference coming to an abrupt end.
Advert
KSI and Fury returned to the stage for a face-off, though the other two competitors swiftly left the building.
But things erupted again when they both went head-to-head and KSI pushed his rival back, leading to John trying to get to the Sidemen member.
Security were just about able to hold him back - albeit knocking off his cap - and ensure that another brawl did not ensue live on DAZN.
The main event is happening at 183lbs, with no rehydration clause. Fury has been advocating for the encounter to be an eight-rounder, however KSI is adamant that it will be a six-round affair.
Advert
KSI's last bout was a controversial one as he knocked out Joe Fournier in May, only for the decision to be turned into a no contest after footage showed he landed a blow with his elbow during the finishing sequence.
His record is therefore 5-0, while the undefeated Fury recorded a ninth consecutive victory when he beat Jake Paul in Saudi Arabia in February.
Featured Image Credit: DAZNTopics: KSI, Tommy Fury, John Fury