Weir was born in Cambridge, England to Scottish parents. While she was still at school she trained with the composer John Tavener. She played the oboe in the National Youth Orchestra of Great Britain. She then studied at the University of Cambridge where her teacher was Robin Holloway.
Judith Weir’s music has harmonies which are very exciting and original. Her Christmas carol Illuminare has become very popular, but it is quite difficult and needs a good choir to pitch the notes of the dissonant chords. She often uses medieval history as inspiration for her music, as well as music from her native Scotland, e.g. piobaireachd, which is a kind of variation form using small intervals. Her music often tells stories. Her operas include A Night at the Chinese Opera, The Vanishing Bridegroom, Blond Eckbert, and Armida, an opera for television.
From 1995 to 2000, she was the Artistic Director of the Spitalfields Festival in London. She has composed works for the City of Birmingham Symphony Orchestra. She has received many honours, including the CBE in 1995.