Warren, who endorsed Clinton last week in an interview, mingled with aides, took photos with staffers and gave brief remarks.
"Don't screw this up," Warren said, according to attendees.
The senator also referred to Clinton as a "fighter," the same terminology she used when she endorsed Clinton last week.
"We've got one tough cookie who is going to be out there fighting on behalf of working families across this country," Warren said in her remarks, according to a video posted on Instagram.
Clinton was not at campaign headquarters when Warren visited, according to aides.
This sort of visit by a notable politician is not abnormal for the Clinton headquarters. Julian Castro and Tom Perez, two cabinet secretaries who are also being eyed for the VP job, have visited in the last few months. As has former president Bill Clinton, Rep. Charlie Rangel, former Vermont Gov. Howard Dean and former Texas State Sen. Wendy Davis.
Warren was already in New York for fundraising meetings of her own, a person close to Warren told CNN.
Warren addressed Clinton staffers in the bullpen area of the Brooklyn headquarters and took pictures with staff.
She did not have any meetings with high-level staffers, one aide said.
Warren is among the Democratic lawmakers being considered for Clinton's vice presidential slot, but aides have said the process is still in the early stages.
A senior Clinton adviser downplayed any tea leaf reading about VP prospects, noting that a public meeting at campaign HQ would be the worst way to keep a secret.
That said, it's part of the tease and suspense. Warren was hailed as a star for getting under Donald Trump's skin in recent weeks with her tweets.
Warren had held off endorsing Clinton during her primary with Vermont Sen. Bernie Sanders, a decision that drew the ire of some of her colleagues in the Senate. But once Clinton won California and New Jersey primaries and racked up enough delegates to clinch the nomination, Warren backed Clinton.
"I'm ready to get in this fight and work my heart out for Hillary Clinton to become the next president of the United States and to make sure that Donald Trump never gets any place close to the White House," Warren told MSNBC's Rachel Maddow.