Florence Susan Harrison was born aboard the SS. Windsor Castle on 2 November 1877, the second daughter of Master Mariner Norwood Harrison (1834-1917) and his wife Lucy Susan (née Thomas, d.1912). The ship, which had 366 immigrants onboard, had departed London on 8 June 1877 and arrived at Brisbane (Port Moreton) in Australia on 18 September 1877. The ship set sail for the return voyage on 10 December 1877. An elder sister, Edith Alice, had been born in Elham, Kent in spring 1876. Edith potentially died onboard SS. Windsor Castle or whilst the family were in Australia, as no British death record has been found for her. At the time of the 1881 Census, the family were staying - probably between voyages - with Florence's great-aunt Elizabeth Harrison at her school for girls at Rockhill House in Hythe, Folkstone. Florence's three brothers were also born in Folkstone: Arthur, Godfrey Edmund (b.1881, who later moved to Melbourne, Australia) and Hugh. Norwood retired from active duties in 1882; he went on to write three books and was appointed a Fellow of the Royal Geographical Society.

In the 1901 census the family were living in Leyton. It is likely Florence spent some time in Bruges, but her exact whereabouts during the First World War are unknown. She was certainly living in London from 1922 onwards. She began work as an illustrator in 1905, illustrating her own books of poetry for children which were published by Blackie. She began to illustrate Romantic literary texts in 1910 and contributed to many popular annuals. She continued to work until the early 1940s when she moved from London to Hove to care for her cousin Mary. She died, in Hove, on 5 January 1955.

For some years, Florence Harrison had been conflated with an artist named Emma Florence Harrison who had exhibited several paintings at the RA between 1887-1891. As such, Mary Jacobs, who had begun collecting examples of Harrison's work, originally attributed the work to Emma Florence until she published an account of Emma's life on a website dedicated to her collection of Florence Harrison's original artwork. She was soon contacted by descendants of Florence's brother Godfrey who provided evidence that it was a case of mistaken identity and Mary subsequently updated her website following her new research into Florence's life.