Kathleen Rollins Snavely was born as one of three siblings to Patrick and Ellen Hayes in Garraun, near Feakle, County Clare, Ireland, United Kingdom (now Republic of Ireland), on 16 February 1902. She emigrated to the United States in 1921 to live with her uncle in Syracuse, New York.

She married Roxie Rollins in 1924, and they were married for 44 years. They set up the Seneca Dairy, which was a successful business and popular ice cream parlour. Rollins died in 1968, and Kathleen married a second time to Jesse Snavely in 1970. Jesse died in 1988. She had no children.

She became the longest-lived person from what is now the Republic of Ireland on 10 January 2014, at the age of 111 years, 328 days, when she surpassed the age of Katherine Plunket (1820–1932). She became the longest-lived person from the island of Ireland on 26 March 2015, at the age of 113 years, 38 days, when she surpassed the age of Annie Scott (1883–1996).

Kathleen Snavely died in a nursing home in Syracuse, New York, USA, on 6 July 2015, aged 113 years, 140 days.