The one-off concert, organised by two leading human rights charities, will feature the London premiere of a new choral work by Emmy-award winning composer Richard Blackford.
Juliet Stevenson, comedian Jeremy Hardy and Tony Harrison have also agreed to appear at the event which aims to raise awareness about refugees and the experiences that force them to flee their native country.
Shaw, who is currently filming in Ireland, said she was delighted to be taking part and added: "I do think that anything which helps these most delicate and sadly relevant charities is a good thing."
Blackford's composition, Voices of Exile, is drawn from poems and stories written by refugees from 16 different countries. It has been commissioned and will be performed by the Bournemouth Symphony Chorus and a 20-piece ensemble drawn from Bournemouth Symphony Orchestra.
Soloists include Robert Tear and Paul Whelan, while Neville Creed will conduct.
The gala, which will take place on November 19, has been organised by the Medical Foundation for the Care of Victims of Torture and the Prisoners of Conscience Appeals Fund.
