The theatre has two auditoria, and is led by Steve Mannix (Executive Director & CEO).

The Mercury Theatre, designed by Norman Downie, was opened on 10 May 1972, after a successful fund-raising campaign, supported by a large grant from the Borough Council.

Adrian Stokes joined as Associate Director in 1995 and initiated the Community Education Programme.

In 1998 Dee Evans arrived as Chief Executive and Gregory Floy as Artistic Producer.

Productions at the Mercury have included the work of John Cleese, Martin Clunes, Gwen Taylor,[8] Simon Gray, Toby Longworth, Ingrid Lacey, Michael Grandage, Mike Poulton, Michael Deacon, Colin McCormack, David Oakes, Donald Freed Michael Grandage made his directorial debut at the Mercury with "The Last Yankee",[9] and Trevor Howard began his career at the Colchester Repertory Company.