Petrosky was born in Astoria, New York, on 14 January 1913. After the death of her husband, she moved to Greenville, New York with her sister. She worked at Bloomingdale’s, a luxury department store chain, for over 40 years, and was also a hairdresser.

Petrosky moved into a nursing home in Albany, New York, in 2014. She joked that her secret to longevity was “pick the right parents.” As a centenarian, her favorite pastimes included fishing, drinking the occasional beer, and spending time with friends and family. On her 110th birthday, Kathy Sheehan, the mayor of Albany, proclaimed 21 January as “Mary Petrosky Day”.