A U.S. adoption agency representing the Hollywood star filed the papers at Vietnam's International Adoption Agency, said Vu Duc Long, the agency's director.
"She just filed the papers this week," Long said.
Jolie and her superstar partner, Brad Pitt, have three children: 5-year-old Maddox, adopted from Cambodia; 2-year-old Zahara, adopted from Ethiopia; and another daughter, Shiloh, who was born to the couple in May.
Long would not name the U.S. adoption agency working with Jolie, who applied to adopt as a single parent.
Jolie and Pitt made a surprise visit to Vietnam at Thanksgiving, when they visited the Tam Binh orphanage, on the outskirts of Ho Chi Minh City.
Their pictures were splashed across the front page of Vietnamese newspapers, showing the couple cruising around Ho Chi Minh City on a motorbike.
Nguyen Van Trung, the director of the Tam Binh orphanage, declined to comment. He said he was awaiting the papers from the International Adoption Agency.
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