Followill warned audience members at a gig in Dallas that he was "about to fall down", before slinking backstage to "vomit" and "drink a beer".
"My voice is completely 100 percent wrong," Caleb can be heard saying in footage posted online. "I'm sorry... Do you know what? I'm going to drink some beer and I'm going to drink some tequila and I'm going to have a good time, and for the record I'm not drunk... I'm just f**king hot."
The 29-year-old, who married model Lily Aldridge in May, continued: "I'm about to fall down here because I'm so goddamn hot. I have no goddamn idea what the f**k is going on, all I know is that I'm married to the prettiest f**king girl in the whole world.
"I'm gonna go backstage for a second. I'm gonna vomit, I'm gonna drink a beer and I'm gonna come back out here and I'm gonna play three more songs."
His brother Jared was then forced to apologise for Caleb's premature exit and opted to cut the show short, saying: "We are so unbelievably sorry, there's no words right now, honestly it's beyond our control.
"Caleb's just maybe a little unfit to play the rest of the show. We're so sorry guys, we love you all so much. I know you guys f**king hate us, I can't apologise enough.
"It's really not our fault. He can't play the rest of the show. We will be back as soon as possible. F**king hate Caleb, not us."
Jared continued to express his regret for the chaotic gig on Twitter, writing: "Dallas, I cannot begin to tell you how sorry I am. There are internal sicknesses & problems that have needed to be addressed. No words."
Caleb hinted last month that Kings of Leon may take a break in the near future.
Watch Caleb Followill's outburst at Kings of Leon's Texas show: