Warren painted Trump as "a man who cares only for himself" and described him as a "a man who must never be president of the United States of America."
"His whole life has been taking advantage of a rigged system," she said, assailing what she said were failures as a businessman and called his immigration plan "a stupid wall."
The crowd appeared to turn on Warren at several points in the speech, however, particularly when she endorsed Clinton.
She called the former Secretary of State one of "the smartest toughest most tenacious people on this planet, and "a woman who fights for all of us."
"I'm with Hillary," she announced.
Some people in the crowd booed Warren during her endorsement.
Protesters chanted "we trusted you" and "Goldman Sachs" during her appeal for Democrats to vote for Clinton.
Warren, whose endorsement was heavily sought after during the primary between Sanders and Clinton, due to her popularity among Democrats, has had a complicated relationship with Clinton.
In 2004, she gave an interview with Bill Moyers in which she described the degree to which she perceived money to influence Clinton when she was a senator representing New York. Sanders supporters seized on the video, and shared it as a kind of anti-endorsement of Clinton's campaign to be the party's nominee.
In June, Warren formally endorsed Clinton and made a joint speech with her in Ohio. Her primary focus in that speech was criticizing Trump.
Warren and Trump have been pitted against each other for a while.
Trump has repeatedly mocked her with the nickname "Pocahontas," a reference to her claim of Native American status during her time in academia, and has called her "goofy Elizabeth Warren."
Warren, for her part, has received plaudits for her willingness to defend herself and Clinton against Trump's rhetorical attacks. She has called him "weak" and a "loser."
“Your policies are dangerous. Your words are reckless. Your record is embarrassing. And your free ride is over,” she tweeted in May.