Jessie Iris Martin was born in Wellington on 19 December 1898, the daughter of Harriet Wilhelmina Warnes and her husband, William Lee Martin, a storeman who later farmed at Matangi near Hamilton and became MP for Raglan (1927–31 and 1935–43). After working for a time in the office of the local dairy factory, Iris (as she was known) went to Wellington Hospital to do her nursing training. In the state final registration examinations of June 1929 she was one of three who gained top equal marks and in 1930 she was the second recipient of the Frances Keith Payne Memorial Medal.
Her potential for teaching and administration was soon recognised, and with a bursary from the Wellington Hospital Board she completed the diploma in hospital administration and teaching in August 1930. Over the next six years she consolidated her education and experience at Wellington Hospital, rising to the position of ward sister. She also obtained leave of absence to complete maternity nursing training at Hastings Memorial Hospital, where in June 1933 she again passed the state finals with honours.
In early 1937, after relieving and nursing in private hospitals and homes, she left for England. During her two years abroad she gained further nursing experience. She also acted as hostess at functions in London for Michael Joseph Savage, the prime minister of New Zealand; was presented at Buckingham Palace; went to the coronation of King George VI; and attended as an observer her first International Council of Nurses meeting. On the way back to New Zealand in late 1938 she travelled via America and Canada, where she studied hospital administration and nursing training methods.
After a year at Cook Hospital, Gisborne, as tutor sister in the nursing programme, she was appointed senior tutor at Waikato Hospital, Hamilton, where she spent a further two years. In February 1942 she took up the position of matron at Cook Hospital.
Contemporaries of Iris Martin remember her strict discipline and adherence to high standards of nursing and behaviour. A short, plump woman, she had a commanding presence as she 'bustled with starched efficiency', making her rounds of wards once and sometimes twice a day. She knew patients and staff alike by name. At times quick-tempered, at others charming, she was respected for improving standards at Cook Hospital.
During her 12 years as matron Iris Martin was active in the Gisborne branch of the New Zealand Registered Nurses' Association and in 1950 was elected to the dominion executive representing the Manawatu area, which at that time included Gisborne. Within a year she was vice president and in 1952 was elected dominion president, a position she was to hold for four years. She represented the association at the International Council of Nurses Quadrennial Congress in São Paulo, Brazil, in July 1953, and at the board of directors meeting in Istanbul, Turkey, in 1955. On both occasions she travelled to other countries to gain information and ideas on hospital and nursing administration systems. After visiting 33 hospitals in eight countries she wrote a comprehensive report, published in 1954, in the hope that it would 'stimulate study and research into Hospital planning, construction and administration in New Zealand'.
Although she retired from her position at Cook Hospital in 1955, Iris Martin was soon in demand. In 1956 she was relieving matron at Greymouth Hospital before taking a six-month position (until April 1957) as temporary matron in chief of the Wellington Hospital Board and matron of Wellington Hospital.
Some months later, Iris Martin joined the Department of Health and spent 10 years working as a public health nurse in Hamilton. She retired from active nursing in 1968. She had been made an MBE for services to nursing in 1955 and was awarded honorary membership of the New Zealand Nurses' Association in 1972.
During her retirement, which she spent with her younger sister Daisy in the family home, she pursued interests in gardening and chamber music. She was also active in the local branch of the Red Cross and the United Nations Association of New Zealand, and continued her lifelong support of the New Zealand Labour Party and the Methodist Church. Iris Martin never married. She died at Hamilton on 19 July 1982.