Janet McTeer was born on August 5, 1961, in Wallsend, Newcastle upon Tyne, England. She is the daughter of Alan McTeer and Jean (née Morris). Raised in York, she attended Queen Anne Grammar School for Girls. Janet developed an early interest in theatre, working at the Old Starre Inn in York and later performing in local productions with the Rowntree Players at the Joseph Rowntree Theatre. Pursuing her passion for acting, she trained at the Royal Academy of Dramatic Art (RADA), one of the United Kingdom's most prestigious drama schools.

Theatre Beginnings and Television Breakthrough

McTeer began her professional theatre career with the Royal Exchange Theatre in Manchester, where she received critical acclaim for her stage work. Her breakthrough in television came with the BBC's adaptation of Portrait of a Marriage, a dramatization of Nigel Nicolson’s biography. In it, she portrayed Vita Sackville-West. Following this, she took a leading role in the ITV series The Governor, created by crime writer Lynda La Plante.

Her film debut occurred in 1986 with Half Moon Street, based on a novel by Paul Theroux. The early 1990s marked continued success, most notably her role in The Black Velvet Gown (1991), which won the International Emmy Award for Best Drama.