Elkin Umbagai was born to Ernie Nyimandum and Ruby Marutja who were leaders for the Kunmunya Mission. Umbagai was educated on Kunmunya Mission and could read and write in both English and Worrorra language. She was the first Girl Guide in Western Australia to be awarded her linguist's badge. After Kunmunya closed in 1956, the Umbagai family and others established the Mowanjum Aboriginal Community near the township of Derby, Western Australia.
Umbagai became an important Aboriginal leader, instructor in research fields such as linguistics, anthropology and archaeology and writer of Aboriginal history and stories. In 1977, the township of Derby named her Grandmother of the Year and in 1978 she was named as one of Western Australia's top 150 women from the time of white settlement.
Her brother was artist and community chairman Alan Mungulu. Her daughter is Heather Umbagai.