Players threw fists and helmets during scuffles leading up to the final free-for-all. Rams defensive star Aaron Donald was thrown to the ground as he clutched a Bengals helmet in each hand.
Donald was also seen swinging a helmet and after the brawl ended he continued yelling at Bengals players. He did not speak to the media after the practice.
Bystander video captured the fight.
"I just see guys swinging and some guys have helmets on, some don't," Rams coach Sean McVay said. "There's a scrum. You just never know what can occur. And my biggest concern is just unnecessary injuries for people that we're counting on, whether it's for our team or the other team."
"It just got a little scuffley," said Bengals coach Zac Taylor.
"We just called it," Taylor said. "We were in the last [practice] period. We got two really good days of work. So was worth getting the extra couple of plays? No. So we called it."
The melee occurred between the Bengals' offense and the Rams' defense.
The Bengals and Rams, who played in the Super Bowl in February, face each other in the final preseason game on Saturday night in Cincinnati.
ESPN and the Associated Press contributed to this report.