Jolie, who is a goodwill ambassador for the United Nations High Commissioner for Refugees, made the visit during a two-day trip to the region, the U.N. refugee agency said Tuesday.
The statement said the 32-year-old actress met with displaced Iraqis in neighboring Syria on Monday before crossing into Iraq for a few hours Tuesday "to see firsthand the plight of hundreds of thousands of families uprooted by the ongoing conflict."
"I have come to Syria and Iraq to help draw attention to this humanitarian crisis and to urge governments to increase their support for UNHCR and its partners," the Geneva-based agency quoted Jolie as saying.
Jolie traveled to the Al-Waleed refugee camp on the Iraqi side of the border and spoke to some of the 1,200 Iraqis living there before visiting a contingent of U.S. troops in the area, the agency said.
Jolie has worked with UNHCR since early 2001. In May, a foundation set up by Jolie and her partner, Brad Pitt, donated $1 million to help those affected by the conflict in Sudan's Darfur region and neighboring Chad.
The U.N. refugee agency estimates that more than 4.2 million Iraqis have left their homes, most of them since the 2003 U.S.-led invasion to topple Saddam Hussein. Of these, about 2 million have fled to neighboring countries, including Syria, Jordan, Egypt and Lebanon.
According to UNHCR, thousands of Iraqis continue to stream into Syria every day, placing a heavy strain on the country's housing, health care and education sectors.
Last month the agency and UNICEF launched an appeal for nearly $130 million to help provide education to displaced Iraqi children across the Middle East. The U.S. said Tuesday it would contribute $30 million to the appeal.