The protesters demanded that Congress reject the deal.
On July 14, Iran and the P5+1 group, comprising China, France, Russia, the United States, the United Kingdom and Germany, reached an agreement to ensure the peaceful nature of Iran's nuclear program in exchange for the easing of sanctions against the country.
US Congress now has until September 17 to decide whether or not to approve the deal.
Congress has been divided on the issue, with Republicans threatening to do their best to scrap the agreement.
The activists argue that the deal with Iran puts the United States and its allies at risk. They also claim that the agreement is undemocratic, as the deal was put forward by Obama without congressional input.
Israel has long been opposed to a nuclear deal with Iran because it holds that should Tehran manage to build or acquire nuclear weapons it will become a threat to global security.