Jolie took the stage to praise the Geneva-based agency and Yemen's Society for Humanitarian Solidarity, which won the agency's top annual award for helping thousands of Somali refugees and migrants who flee for Yemen in smuggler's boats across the perilous Gulf of Aden.
"The desperation fueled by a vicious combination of drought, famine and conflict has driven tens of thousands of people from the Horn of Africa," Jolie said.
"And we must not forget what is happening in this part of the world," she said. "We must try to imagine how desperate these people must be, when their only alternative is to risk death at sea and put their lives in the hands of ruthless smugglers."
Somalia has had transitional administrations for the past seven years. But it has lacked a functioning central government since 1991, when warlords overthrew a longtime dictator and then turned on each other, plunging the impoverished country into chaos.
The transitional government, backed by African Union troops, has been fighting against al-Shabab insurgents — Islamic militants who abandoned Mogadishu in early August but still hold much of southern Somalia, where tens of thousands are believed to have starved to death and tens of thousands more have fled or tried to flee in the hope of finding food.
Jolie said the 290 staff of the Society for Humanitarian Solidarity, as well as its founder Nasser Salim Ali Al-Hamairy, deserve much credit for risking their own lives to save thousands of others each year.
She said she looked forward to representing the UNHCR and its staff for another 10 years.
"Most of all I'm so grateful — I don't want to cry — to the refugee families that I have the honor and privilege to spend the last years with," she said.
"From them I've learned so much. I've learned to be a better person, a better mother. They've inspired me by showing me the unbreakable strength of the human spirit."