Nerli was born in Siena, the son of a minor Italian aristocrat and an English woman. He studied art in Florence and went to Australia in 1885. There he was associated with the Heidelberg painters and was an important influence on Charles Conder. He settled in Dunedin, New Zealand, in 1893 where he opened a private art academy and again inspired a generation of young artists, including Frances Hodgkins. After eloping with a local woman, he returned to Australia but was unable to re-establish himself. In 1904 the artist and his wife returned to Europe, where he spent the remaining years of his life in relative poverty.