Since December nearly 200 000 people have sought refuge from sectarian violence in neighbouring countries, and that figure is expected to rise to over 360 000 by the end of the year, the UN refugee agency said.
About 600 000 people are displaced inside the CAR.
"The mainly women and children fleeing atrocities in CAR are arriving in neighbouring countries deeply traumatised, many wounded by machete or gunshot, malnourished and exhausted from weeks of walking and hiding," the agency said.
"All the agencies working in the region are dramatically underfunded," the UN High Commissioner for Refugees, Antonio Guterres, told diplomats in Geneva.
Guterres said his agency is already spending three times as much as it has received so far. "This cannot be sustained," he said.
Last week, the UN Security Council authorised a nearly 12 000-strong peacekeeping force to bolster French and African Union troops that have been deployed to protect civilians throughout the vast country.
The money sought by the UN refugee agency and 14 other humanitarian organisations will be used to pay for shelter, food, water, sanitation, health care, education and basic needs.