Nellie Mooney was born in Nowra at the Edman Private Hospital in 1938. She was the second youngest of eleven children, and her mother passed away when she was two years old. Mooney's father worked on a farm as a slaughterer and the family lived in a house on the property. This meant that the children were not targeted for removal by the Welfare.

Mooney has served as Chairperson of the Aboriginal Student Support and Parent Awareness (ASSPA) committee and Chairperson of the local Aboriginal Education Consultative Group (AECG). She has sat on the regional Aboriginal Education Advisory Committee and served as Chairperson for the Local Aboriginal Land Council for 11 years. In 1993 Mooney received a citation from the Education Department for outstanding services to the local schools.