The actress is a special envoy for the United Nations High Commissioner for Refugees and paid a visit to the Zaatari camp, which houses 27,000 people in Jordan.
She delivered a speech expressing her concern at the situation, and described hearing local stories as "horrific".
In an emotional talk, she said: "I am very concerned, the world is very concerned. What is very heartbreaking is when Syrian people ask you why you think no-one is able to find a solution for them.
"What they described on the ground, hearing it from them is so horrific. When you meet so many innocent people and civilians, the people of Syria are asking who is on their side, 'Who is going to help us as the months go on?'"
The 37-year-old star, who has six children with Brad Pitt, has visited a number of international trouble spots in her role at the UN.
In 2001, she spent 18 days in Sierra Leone and Tanzania.
More recently she took trips to Iraq, Chad and Afghanistan to bring attention to problems there.