The Hollywood star grabbed a megaphone on the streets of Los Angeles, joining a rally for the release of 276 girls who were kidnapped by Islamic terror group Boko Haram.
Husband Adam Shulman joined the star, as she held a heart-shaped placard reading "Bring Back Our Girls," in keeping with a social media campaign of the same name.
She said through a megaphone: "These Nigerian girls are part of a 5 percent of girls who are able to seek an education. They were taken from their beds in the middle of the night by cowards who tell them that girls do not deserve an education."
Meanwhile, Michelle Obama has got involved in the social media drive, tweeting a photo of herself with the hashtag #BringBackOurGirls.
Kim Kardashian, Amy Poehler and Leona Lewis are also among the stars who have tweeted similar pictures.
Bob Geldof has also spoken out against the kidnappings, saying: "At the heart of this is a fanatical ideology that is repulsive, of course, but when it attacks school girls, the world wants to throw up."