On the US National Mall, several hundred men and women of all ages - donning green, white and red, the colors of the Iran flag - chanted.
"Be scared. Be scared. We are one in this," some shouted, ahead of the group's march to the White House on Saturday. "Say her name! Mahsa!"
The demonstrations, put together by grassroots organisers from around the United States, drew Iranians from across the Washington DC area.
The Biden administration has said it condemns the brutality and repression against the citizens of Iran and that it will look for ways to impose more sanctions against the Iranian government if the violence continues.
In Tehran, more anti-government protests took place Saturday at several universities.
The nationwide movement in Iran first focused on the country's mandatory hijab covering for women following Amiri's death on September 16. The Iranian protests have since transformed into the greatest challenge to the Islamic Republic since the 2009 Green Movement over disputed elections.
Iran's security forces have dispersed gatherings in that country with live ammunition and tear gas, killing more than 200 people, including teenage girls, according to rights groups.
In Berlin, nearly 40,000 people gathered in solidarity with the women and activists leading the movement for the past few weeks in Iran.
The protests in Germany's capital began at the Victory Column in Berlin's Tiergarten park and continued as a march through central Berlin.
Several weeks of Saturday solidarity rallies in the US capital have drawn growing crowds.
