Irene Gepfert Mertz was born in Fort Wayne, Indiana on 13 October 1919. She was one of seven siblings. After both parents died she and most of her siblings became wards of the state. Mertz spent her childhood in Fort Wayne and finished high school there. She then studied at the School of Nursing St. Joseph's Hospital in Fort Wayne, Indiana. After completing her studies, she worked at St. Joseph's Hospital for three months as the charge nurse supervisor of the orthopedic ward.

Mertz was commissioned into the Navy Nurse Corps on 10 May 1943 and was assigned to San Diego United States Naval Hospital in California. In early 1944, she was transferred to Aiea Heights United States Naval Hospital in Hawaii where she worked as a ward nurse. During this time, she appeared on the radio broadcast "Your Hoosier Marines" where she and one of her marine patients were interviewed about their backgrounds and their daily routines at Aiea Heights United States Naval Hospital. One of her notable patients was posthumous Navy Cross recepient Major Roger G.B. Broome, whose actions during the war warranted a visit from President Franklin D. Roosevelt to the hospital where Mertz was working. On 1 March 1945, she was promoted from ensign to lieutenant.

After the war, Irene married Richard Mertz, and they lived in North Carolina for many years. She passed away in December 2012.