Pleasence was born in Chapeltown, Sheffield, West Riding of Yorkshire, to Miriam Raymond and actor Donald Pleasence. She studied at the Royal Academy of Dramatic Art, and made her stage debut in 1964 as Titania in a production of A Midsummer Night's Dream at the Birmingham Repertory Theatre. She appeared extensively in London theatre productions throughout the 1970s.
She is also noted for her roles in horror films of the 1970s, including From Beyond the Grave, Symptoms and The Godsend. She made a guest appearance in the parody series Dr. Terrible's House of Horrible satirising her earlier performances.
She worked extensively in television productions and British miniseries throughout the 1980s and 1990s. She had minor roles in the films The Search for John Gissing (2001), Gangs of New York (2002), and The Gigolos (2005).
Two other roles are the Ghost of Christmas Past in the 1984 holiday television film A Christmas Carol and a role as a crowd member in Martin Scorsese's 2002 crime drama Gangs of New York.
She also appeared in Stealing Heaven (1988) and appeared in "The Shakespeare Code" episode of Doctor Who as Elizabeth I.
She appeared as Winnie in the BBC drama Happy Valley (2016).
