Sarah McCartney was born in Devon. She obtained a BA (Hons) in Sculpture from Kingston Polytechnic in 1986. This was followed by a postgraduate diploma in Sculpture from the Royal Academy Schools. In 2022 she completed an MA in Authorial Illustration at Falmouth University. She has also undergone courses in blacksmithing, ceramic shell bronze casting, chain saw training and botanical illustration.

McCartney has lived in Cornwall and has worked for the Cornwall Wildlife Trust as a graphic designer and illustrator since 1992. She has carried out commissions in illustration and sculpture for clients including Thomas Cook in Berkeley Street, London, the Royal Cornwall Museum, National Maritime Museum, Isles of Scilly Steamship Group and Royal Yachting Association. Her work has been on show in London, Oxford and Berlin, and she has exhibited widely in Cornwall.

Her work was included in the Cornwall Wildlife Trust's collection of non-native species, on display at the London Boat Show in February 2015, to raise awareness of the growing danger to the UK's marine life.