"I am ready to get into this fight," Warren said.
"Hillary Clinton won, and she won because she's a fighter," Warren added. "She's out there, she's tough. And I think this is what we need."
While Warren's name has been floated as a potential running mate for Clinton, the Massachusetts senator said "no" she has not heard from Clinton or her campaign about whether she is under consideration for the position and added that she loves her current job.
“I think that it’s clear now that we need to start thinking about all of us together and we need to think about the difference between us and the difference between the Republicans,” Warren said.
"The Republicans underestimated and underestimated and underestimated Donald Trump. Look where that got them. They kept saying, no, no, no, that's not going to happen, we don't have to worry about that," she said. "Donald Trump is a genuine threat to this country. He is a threat economically to this country. But he is a threat to who we are as a people. There is an ugly side to Donald Trump that we all have to stop and think about what's going on here. "
The announcement comes on the same day that President Obama endorsed Clinton as the presumptive Democratic nominee, after she secured enough delegates to clinch the party's nomination earlier this week.
On Tuesday night, during an exclusive interview with ABC News shortly before giving her acceptance speech, Clinton praised Warren and didn't rule out the prospect of having her on her ticket as vice president.
"I'm not going to get into vice presidential choices, but I have the highest regard for Sen. Warren," Clinton said.