"Around 170,000 Yemenis, refugees and third country nationals have fled to Djibouti, Ethiopia, Somalia, Sudan and some Gulf countries," the UN refugee agency (UNHCR) and International Organization for Migration (IOM) said in a statement, after aid meetings in the Kenyan capital.
The UN said it needed over $94 million (86 million euros) to support those fleeing the war in 2016.
Signup to our newsletter and follow us on Facebook and Twitter!
Thousands have been killed and the impoverished nation plunged into profound humanitarian crisis since March, amid battles between pro-government forces supported by Saudi-led air strikes and Iran-backed rebels.
Most of the refugees have made a "perilous crossing" across the Gulf of Aden to the Horn of Africa, said Claire Bourgeois, who heads UN refugee agency operations for those fleeing Yemen.
Inside Yemen, an estimated 80 percent of people need aid, including 2.3 million forced from their homes, the UN said.
"The suffering that this conflict is inflicting on people is heart-breaking," Bourgeois said.