The rallies took place on Friday as people across the country marched, chanting slogans and holding placards in support of the IRGC.
The demonstrations came after numerous expressions of support by the Iranian public and different political factions were made for the military organisation.
Rallies in Tehran ended with the recitation of a statement condemning the American move.
It also called for the further bolstering of Iran’s armed forces and defense capabilities in the face of American “government-sponsored terrorism” in the region.
“We call on the judicial, parliamentary and executive branches along with other authorities to adopt strict measures for an all-out resistance,” read part of the statement.
The protesters also called for the continued assistance of foreign nations facing US and Zionist aggression.
Addressing worshipers at weekly Friday prayers, Tehran interim Friday prayers leader Ayatollah Mohammad Ali Movahedi Kermani denounced the US measure.
Ayatollah Kermani referred to statements made by US officials implicating that Washington had effectively helped in the formation of numerous terrorist groups such as Daesh, saying "the US is the mother of terrorism."
Ayatollah Kermani also highlighted the IRGC's role in countering terrorist groups in the region, describing the US blacklisting as "comical".
On April 8, US President Donald Trump blacklisted the IRGC, which helped the national armies of Iraq and Syria rid their countries of Daesh terrorists in late 2017.
Saudi Arabia has openly lauded Trump's decision. The United Arab Emirates, a close ally of both the US and Saudi Arabia, has been known to take hostile actions against the IRGC in the past. Israeli Prime Minister Benjamin Netanyahu also thanked Trump for his move against the IRGC.
Following Trump’s declaration on Monday, Iran reciprocated by designating the US Central Command (CENTCOM), the portion of the US military responsible for protecting American security interests in the Middle East and the Horn of Africa, as a terrorist organization.