The actress, who is known for her humanitarian work, especially her efforts to aid Syrian refugees, penned the scathing op-ed for the New York Times.
In the piece, she urged that policy decisions should be based on "facts, not fear," and invoked former President Ronald Reagan in her opposition to the ban.
"The global refugee crisis and the threat from terrorism make it entirely justifiable that we consider how best to secure our borders," she wrote.
"Every government must balance the needs of its citizens with its international responsibilities. But our response must be measured and should be based on facts, not fear."
"It is simply not true that our borders are overrun or that refugees are admitted to the United States without close scrutiny,"
"If we create a tier of second-class refugees, implying Muslims are less worthy of protection, we fuel extremism abroad, and at home we undermine the ideal of diversity cherished by Democrats and Republicans alike:
'America is committed to the world because so much of the world is inside America,' in the words of Ronald Reagan."
The actress is a special envoy of the United Nations High Commissioner for Refugees.
Trump signed the controversial executive order on Friday, and Hollywood at large has been vocal in its criticism of the ban.