Instead, in an appearance on NBC's "Meet the Press," the Kentucky Republican would only say he "couldn't disagree more" with Trump's comments.
McConnell also acknowledged he is concerned that Trump could alienate Latino voters -- tipping Latinos into Democrats' camp and causing the Republican Party a similar problem to the African-American exodus to Democrats after the party's early-1960s standard-bearer, Barry Goldwater, opposed the Civil Rights Act.
Trump attacked Judge Gonzalo Curiel last week, saying the American-born judge's Mexican heritage create an "absolute conflict" in the civil lawsuits against Trump University and suggesting Curiel's actions in the case have been retribution for Trump's proposal to build a wall along the U.S.-Mexico border.
House Speaker Paul Ryan had already rebuked Trump over those attacks on Curiel, and McConnell did so Sunday.
"I don't agree with what he had to say," McConnell said of Trump.
"This is a man who was born in Indiana," he said of Curiel. "All of us came here from somewhere else. Almost all Americans are either near-term immigrants like my wife, who came here at age 8 not speaking a word of English, or the rest of us whose ancestors were risk-takers who came here and made this country great. That's an important part of what makes America work."
McConnell acknowledged that he is concerned about Latino voters rejecting the GOP.
"America is changing. When Ronald Reagan was elected, 84% of the electorate was white," McConnell said.
"This November, 70% will be. It's a big mistake for our party to write off Latino Americans. And they're an important part of the country and soon to be the largest minority group in the country. And I am concerned about that," McConnell said, answering host Chuck Todd's question about whether he's concerned Trump will leave a stain on the GOP with Latino voters.
"I hope he'll change his direction on that," McConnell said.