Republican House member Mike Rogers had to be physically restrained after lunging at Mr Gaetz amid chaotic scenes on Capitol Hill.
Congressman Richard Hudson, of North Carolina, grabbed Mr Rogers from behind around his face and shoulder and pulled the irate Alabama Congressman away.
The moment of high drama came after the House convened to hold its 14th vote at 10pm on Friday, with Mr McCarthy confident he had secured enough votes to finally become Speaker.
But in a dramatic twist, four House Republicans voted for alternative candidates, while Mr Gaetz and fellow “Never Kevin” agitator Lauren Boebert voted present.
With his hopes of being elected speaker hanging by a thread, Mr McCarthy walked over to where Mr Gaetz and Ms Boebert were seated and began remonstrating with them in full view of the C-Span cameras.
The House fell silent as the GOP leader appeared to plead with Mr Gaetz to switch his vote to “McCarthy”, but the bombastic Florida lawmaker remained defiant.
As a dejected Mr McCarthy walked back to his seat, Mr Rogers then angrily confronted Mr Gaetz, with the pair nearly coming to blows.
“I won’t forget this!” Mr Rogers shouted.
Mr McCarthy then wandered back to try to calm the warring Congressman, before eventually taking his seat.
Mr Gaetz appeared to make fun of the confrontation, flexing his muscle, to the amusement of fellow right-wing Republican Anna Paulina Luna.
When tempers finally cooled, a motion to adjourn the House until Monday morning was put forward.
Just as it appeared that the House speaker election would drag on for several more days, McCarthy allies managed to persuade the four holdouts — Eli Crane, Bob Good, Andy Biggs and Matt Rosendale — to change their votes to present.
Finally taking the gavel after 1am ET on Saturday morning, Mr McCarthy said: “I hope one thing is clear. I never give up.”
He also thanked former president Donald Trump for an 11th hour lobbying phone calls.
Mr McCarthy said afterward that Mr Gaetz had eventually “got everybody there to the point that nobody voted against me,” persuading some of his fellow colleagues to vote “present” as well.