Ellen Margaret "Nelle" Scanlan was born in Picton, New Zealand, to a family of Irish Catholic immigrants. When she was a small child, the family moved to Blenheim, where she attended a convent school. She began writing stories, poetry, and plays around the age of nine. In the late 1890s, the family moved again to Palmerston North, where Nelle worked as a secretary for several years before setting up her own secretarial business. She also began to write short stories and to work as a freelance journalist for the Manawatu Times. When the male journalists went to fight in World War I, she was invited to join the staff and rose to become sub-editor.
In the USA to report on social events and personalities in Washington, D.C., she became well-known as an "ambassador" of sorts for New Zealand, often speaking at women's clubs. Articles she wrote during this time were collected as a book, Boudoir Mirrors of Washington (1923).
During this time, she traveled widely in the USA, Canada, Europe, and East Asia. From 1923 to 1948, she lived in England, where she continued writing fiction and freelance journalism. In 1932, she published Pencarrow, the first novel in the series that became known as the Pencarrow Quartet, followed by Tides of Youth (1933), Winds of Heaven (1934) and Kelly Pencarrow (1939). These books made her the most popular New Zealand novelist of her generation.
In 1948, she returned to live in New Zealand. Her last novel, The Young Summer, was published in 1952. Her autobiography, Road to Pencarrow, appeared in 1963.
She was appointed the MBE in 1965 for services to journalism and New Zealand writing.