In a series of tweets, the Democrat from Massachusetts criticized Trump's past business ventures and his election tactics. Warren said the bombastic mogul "stands ready to tear apart an America that was built on values like decency, community and concern for our neighbors."
When asked about Warren at a press conference Monday afternoon, Trump said, "You mean the Indian?" Trump recently mocked Warren's past claim of Native American ancestry in a New York Times interview, calling her a "fraud."
On Monday, he said Warren, Democratic front-runner Hillary Clinton and others contribute to a "divided" country.
Warren is just the latest political notable, on either side of the aisle, to publicly condemn Trump as he racks up a delegate lead in the GOP primary. His rhetoric and proposals on immigrants and Muslims have drawn bipartisan ire, and most recently he has received criticism for violence at his rallies.
Trump has taken 685 pledged delegates so far, versus 427 for Sen. Ted Cruz of Texas, his closest competitor, according to NBC News. Tuesday's contests in Arizona and Utah will help to determine whether Trump reaches the delegate count needed to win the GOP nomination outright.
Spokespeople for both the Trump campaign and the Trump Organization did not immediately respond to requests for comment.