Mary Hardy was born in Warrnambool and brought up in Bacchus Marsh. The youngest of eight children; her parents were Winifred Mary (née Bourke) and Thomas John Hardy; the author Frank Hardy was her brother. Her professional acting career began in 1950, when she was noticed by J. C. Williamson, where she worked for several years in various productions. In 1957, as Peter in the J. C. Williamson production of "Peter Pan", Hardy first became known as a star, proving to be a huge success.