The boy, Pax Thien Jolie was born in November of 2003, according to People magazine.
The mother and child will spend the next week in Vietnam, while American authorities issue the child a passport.
The boy was living in an orphanage in Tam Binh, near Ho Chi Minh. Jolie is also traveling with her first adopted child, Maddox, who was born in Cambodia. Actor Brad Pitt stayed in Los Angeles where he is working on a film.