During Wednesday's CNBC debate Cain said Pelosi, who in the last Congress served as House Speaker, had held up a healthcare bill that should have been passed.
"Princess Nancy sent it to committee and it stayed there. It never came out. H.R. ... 3,000 allows the decision to be with the doctors and the patients, not with the bureaucrats in Washington, D.C.," said Cain.
Cain was discussing his ideas for reforming the healthcare system in the United States.
"That kind of boorishness that we see on the part of Mr. Cain plays into a narrative that's been out here now for the last two weeks," said Clyburn on MSNBC's "Andrea Mitchell Reports."
"He ought to be very, very careful how he reacts to or treats women going forward and that was a disrespectful comment about one of the outstanding women in our great country," added Clyburn.
Cain's campaign has been mired in controversy since reports of sexual harassment allegations began to surface last week. The GOP hopeful again denied the accusations during last night's debate, saying they are "unfounded."
Clyburn praised Pelosi, saying she "earned" her way into the Speakership.
"I believe for him to denigrate her and her position that way is just unbecoming of a Southern gentleman. ... Us Southern gentlemen just don't act that way," Clyburn said.
Clyburn grew up in South Carolina, attended college there and has represented the state in the House of Representatives since 1993. Cain was raised and educated in Atlanta.
To watch Cain's reference to Pelosi during the debate, click here.