After moving to Coober Pedy to work as a miner in 1969. Cox began her career at the age of 25 working for The Department of Foreign Affairs in 1970. Her first overseas posting was to Phnom Penh in 1971. The country was in turmoil at the time, with the Vietnam war at the border and American B52s dropping bombs. Geraldine refers to this first posting as an experience that significantly shaped who she is today. Her following overseas postings included working for Australian Embassies in Manila (1973-1978), Bangkok (1978-1981), Tehran and Washington D.C. After resigning from the Government in 1987 Cox worked for eight years at the Chase Manhattan Bank in Sydney.