The 31-year-old actress dodged reporters on her way from the airport after flying from Ho Chi Minh City, where she adopted the newest member of her family at an orphanage on the outskirts of the city last week.
Jolie was expected to meet with U.S. Embassy officials Tuesday to apply for a visa for 3-year-old Pax. Once the visa is issued, she can take him to the United States. She was expected to leave Hanoi on Wednesday.
Jolie's oldest child, 5-year-old Maddox, who was adopted from Cambodia, came with her to Vietnam. She also has two daughters: Zahara, 2, who was adopted from Ethiopia, and 9-month-old, Shiloh, who was born to Jolie and her partner, Brad Pitt, in May.
Ever since she was young she has wanted to adopt children, Jolie said in an interview published Friday in a Vietnamese newspaper.
"Everyone would agree that children need to have a family," the paper quoted the Oscar-winning actress as saying. "I have the ability to help children fulfill that desire. Why should I say no?"
• Angelina Jolie Celebrity Center