The protests Monday, on the 14th anniversary of the opening of the prison in Cuba, come a day after the US administration once again vowed to shut down the controversial detention site before President Barack Obama's term ends this year.
The group included a coalition of human rights activists, torture survivors and attorneys.
There are still 103 detainees currently being held at the Guantanamo Bay.
Since the prison opened in January 2002, nine prisoners have died there.
Protesters outside the White House wore orange jumpsuits and plastic shackles. Some of them deployed a large inflatable doll meant to represent former prisoner Shaker Aamer, the Saudi national who was suspected by US authorities of being associated with al-Qaeda but was never charged with any crime.
Protesters outside the White House wore orange jumpsuits and plastic shackles [Reuters]
Aamer was released in October after 13 years of detention and has since returned to Britain where his wife is from.
Denis McDonough, Obama’s chief of staff, claimed on Monday that the president was determined to close the detention centre before his presidency ends in 11 months.
"He feels an obligation to the next president. He will fix this so that they don't have to be confronted with the same set of challenges," McDonough said, Al Jazeera reported.
Obama pledged during the 2008 presidential election campaign that he would close the military prison, which housed foreign terrorism suspects after the September 11 attacks.
The detention centre is a source of controversy as the treatment of the prisoners at the centre has been described as torture by human rights groups, involving methods such as force-feeding and sleep deprivation.
Protesters from Amnesty International USA and other organizations rallied outside the White House [Reuters]