Janet Lindsay "Jenny" Greig was born in 1874 in Broughty Ferry, Scotland, the second of eight children of textile merchant and higher education advocate Robert Greig, and his wife Jane Stocks (née Macfarlane) (1848-1902).

She was educated at the High School of Dundee until the family migrated to Melbourne, Australia in 1889, where she then attended Brunswick Ladies College.

Her father encouraged his children to pursue tertiary education, and in 1891 both she and her sister Jane enrolled at the medical school of the University of Melbourne.

[2] For many years, Greig ran a private practice in Fitzroy, Victoria and worked as a consultant from Collins Street, Melbourne.

[1] In 1940 she was admitted to the Royal Australasian College of Physicians and elected President of the Victorian Medical Women's Society.