"The UN is making preparations for up to 600 UN staff and their dependants to be temporarily relocated to Cyprus on four UN charter flights," UN spokesman Rolando Gomez told AFP.
Some essential staff will remain in Egypt, he said.
Those being evacuated represent UN agencies including the UN Children`s Fund, World Health Organization, the UN Educational, Scientific and Cultural Organization, and the UN High Commissioner for Refugees.
Gomez said the decision was taken by UN headquarters in New York because the security situation in Cairo was deemed "volatile and unstable" despite no attacks on UN staff.
The evacuation is to take place throughout Thursday with the first arrivals at Larnaca airport expected in the early afternoon.
Two aircraft will fly to the Egyptian capital to pick up 148 passengers each, and then refuel at Larnaca before picking up the rest, said airports spokesman Adamos Aspris.
Cyprus has been chosen as a staging post to get foreign nationals out of Egypt with more than 150 US citizens arriving earlier in the week on specially arranged American flights.
Interior Minister Neoclis Sylikiotis has said around 320 people have used Cyprus as a transit point so far. The island, an EU member state, is about 90 minutes` flying time from Cairo.
Cyprus became a safe haven for thousands of foreign nationals fleeing the Israeli bombing of southern Lebanon in 2006 when the biggest sea evacuation since World War II took place.(*)