Geraldine McEwan was born in Old Windsor, England and made her theatre debut at the age of 14 at the Theatre Royal in Windsor. By the age of 18 she was starring in London's West End in several long-running popular productions. During the 1950s she acted with the Shakespeare Memorial Theatre in Stratford-Upon-Avon and joined the Royal Shakespeare Company in 1961.

She had leading roles as Beatrice in Much Ado About Nothing with Christopher Plummer, Ophelia in Hamlet, The Princess of France in Love's Labour's Lost, Marina in Pericles and played opposite Dorothy Tutin in Twelfth Night which also toured Moscow and Leningrad.

Miss McEwan originated the female lead role in Joe Orton's Loot, captivated Broadway with productions of The School for Scandal, The Private Ear and the Public Eye, and most recently, The Chairs, earning her a Tony nomination for best actress.

As a member of the Royal National Theatre, acting along side Albert Finney, and Laurence Olivier, Geraldine spent the 1960s and 70s with memorable roles including The Dance of Death, Love for Love, A Flea in Her Ear, Chez Nous, Home and Beauty, The Browning Version, Harlequinade and The White Devil. In 1976 she had the distinction of being nominated for an Olivier Award in two separate categories.

In 1983 she won the Evening Standard Best Actress Award for The Rivals. In 1991 she won the BAFTA Best Actress Award for her intense and powerful performance as the Mother in Oranges Are Not the Only Fruit and in 1995 she won the Evening Standard Best Actress Award for her performance of Lady Wishfort in The Way of the World.

In 1998, McEwan was nominated for a Tony Award in the Best Actress Category for The Chairs. Her numerous television credits include the highly acclaimed The Barchester Chronicles with Alan Rickman, The Prime of Miss Jean Brodie, Mulberry, and the immensely popular Mapp & Lucia. Her film work includes The Dance of Death with Laurence Olivier, Robin Hood: Prince of Thieves with Alan Rickman, Henry V and Love's Labour's Lost, both with Kenneth Branagh, and most recently The Magdalene Sisters, The Lazarus Child, Vanity Fair and Carrie's War. Currently, Geraldine McEwan is starring as Agatha Christie's Miss Marple in a series of TV movies for PBS Mystery and ITV(UK).
Directed a production of "As You Like It" for Kenneth Branagh's Renaissance Theatre Company when it was first starting. Husband was the Principal of the Royal Acadamy of Dramatic Art in London. She allegedly declined the honour of Dame of the British Empire in 2002. She allegedly declined an O.B.E. (Officer of the Order of the British Empire) in 1986. She was awarded the 1983 London Evening Standard Theatre Award for Best Actress for her performance in The Rivals. She was awarded the 1995 London Evening Standard Theatre Award for Best Actress for her performance in The Way of the World. Became an Associate Member of RADA. Was nominated for Broadway's 1998 Tony Award as Best Actress (Play) for Eugène Ionesco's "The Chairs."