The Ambassadors Theatre was designed by W G R Sprague who designed many West End Theatres including the St Martin's situated next door and the Aldwych Theatre in Covent Garden. It was built by Kingerlee and Sons of Oxford.

The theatre opened on 5th June 1913 with a production of Panthea, a play by Monckton Hoffe which ran for only 15 nights.

The great impresario Charles B. Cochran took a lease on the theatre in 1914 and introduced what was then a new genre of entertainment from Paris, the 'intimate' review. Odds and Ends starring the French actress and singer Alice Delysia ran for over 400 performances. More Odds and Ends followed in 1915.
Vivian Leigh

Subsequently the theatre presented Deburau in 1921 which saw Ivor Novello making his first stage appearance, Eugene O'Neill's The Emperor Jones starring Paul Robeson, The Mask of Virtue in 1935 which saw the West End stage debut of a 22 year old Vivien Leigh and Spring Meeting in 1938 with Margaret Rutherford.

Britain's longest running production The Mousetrap by Agatha Christie opened at The Ambassadors on 25th November 1952 and played here until its 21st Birthday in 1973 when it transferred next door to the larger St Martin's Theatre. The stalls bar of the Ambassadors currently displays a commemorative statuette, which was presented to the theatre by Agatha Christie to celebrate the play's record breaking run.
The Mousetrap

Following The Mousetrap the theatre saw a variety of shows, the most notable at this time was the RSC's hit production of Les Liasions Dangereuses by Christopher Hampton with Alan Rickman.

In 1996 the theatre was transformed into two studio spaces to accommodate the Royal Court Theatre Upstairs who were resident until 1999. After their successful residence the theatre was converted back to its original design and renamed The New Ambassadors Theatre.

Since 1999 the theatre has seen many shows play at this intimate venue including: Some Explicit Polaroids by Mark Ravenhill, Spoonface Steinberg by Lee Hall, Krapp's Last Tape by Samuel Beckett and starring John Hurt, Al Murray the Pub Landlord, Marie Jones' award winning Stones In His Pockets, The Vagina Monologues by Eve Ensler, The Watermill Theatre's highly acclaimed production of Stephen Sondheim's Sweeney Todd and On The Third Day – winner of the Channel Four search for a first time playwright entitled The Play's The Thing.

Most recent productions at the theatre have been Love Song by John Kolvenbach starring Cillian Murphy and Neve Campbell, the political comedy Whipping It Up by Steve Thompson and starring Richard Wilson and Robert Bathurst and the Menier Chocolate Factory's revival of Little Shop of Horrors. The current production of Stomp opened in October 2007.

In June 2007 the theatre reverted back to its original name of The Ambassadors Theatre.