Alethea Garstin was born in 1894 in Penzance, Cornwall. She is the daughter of Norman Garstin, the Newlyn School artist. She learnt to paint at a young age and exhibited her first painting, 'The Chairmakers', at the Royal Academy in 1912. She exhibited regularly. Her most notable exhibition being the solo exhibition at the Adams Gallery in 1945, where she showed sixty works.

She was influenced by the fauvist painters. She preferred working on a small scale and painting en plein air directly onto board. In 1978, Patrick Heron referred to Alethea as 'England's leading Impressionist painter' and 'as good as Vuillard'. Alethea Garstin passed away in 1978.

Alethea Garstin (1894-1978) Daughter of the Limerick artist Norman Garstin (1847-1926), she painted from childhood and had her first picture hung at the Royal Academy when she was a mere eighteen years of age. She travelled the world in search of artistic subject matter, often accompanied by either her father or by Dod Proctor.

She is best remembered for her contribution to the Newlyn School of painting. A retrospective exhibition was held in Dublin at the National Gallery in 1978, the year of her death, while more recently the Molesworth Gallery exhibited works from her studio.