The actor, 71, was part of the rally which took place inside a Senate office at the Department of Justice in Washington.
She walked among the crowd who held signs denouncing the president's “zero-tolerance” policy following distressing scenes at the US-Mexico border which has seen crying children torn from their parents in recent weeks.
It's been reported they were shouting “we care” in reference to the H&M jacket worn by Melania Trump ahead of her visit to a detainment centre on the border last week.
The women - who bellowed anti-Trump chants in unison - were arrested, charged and released.
Sarandon was criticised for supporting Green Party nominee Jill Stein over Hillary Clinton following Trump's election win. She later branded his former Democrat rival “very dangerous” in a Guardian interview.
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