[2] Cornwell began her career as an actress, making her debut for Richard Cottrell's Cambridge Theatre Company in November 1971 as Miss Brewster in Arthur Wing Pinero's Trelawny of the 'Wells'.
[2] Charlotte credited her brother David with suggesting she pursue a career as an actress, and at his prompting, she auditioned and earned a place at the Webber Douglas Academy of Dramatic Art (WDADA) in London.
[8] After completing her education at the WDADA, Cornwell began her career as an actress, making her debut for Richard Cottrell's Cambridge Theatre Company in November 1971 as Miss Brewster in Arthur Wing Pinero's Trelawny of the 'Wells'.
[9] She remained a member of the Bristol Old Vic Company through to 1975, playing a broad range of roles from Kate Hotspur in Shakespeare's Henry IV to Becky in Sam Shepard's The Tooth of Crime and Queen Elizabeth I in Robert Bolt's Vivat!
[13] While working at the Bristol Old Vic, Cornwell made her screen debut in the small role of Sally Potter in the 1974 musical film Stardust.
[17] She worked extensively both in the West End and at fringe venues, and appeared in the United States in several productions, including Richard III and An Enemy of the People opposite Sir Ian McKellen, Athol Fugard's The Road to Mecca, Terence McNally's Master Class, Stephen Sondheim's A Little Night Music (San Francisco Bay Critics' Award), and Alan Bennett's The History Boys at the Ahmanson Theatre in Los Angeles.
[18] In a return to staged Shakespeare, in Summer 2016 she was the Chorus in the Regent's Park production of Henry V.[19] Among her film appearances were roles in Stardust (1974), The Brute (1977), The Krays (1990), The Russia House (1990), White Hunter Black Heart (1990), The Saint (1997), Ghosts of Mars (2001) and Dead Space: Aftermath (voiceover, 2010).
[20] Cornwell worked extensively on television including series lead roles in Rock Follies (1976–77) and No Excuses (1983), and appearances in The Men's Room, The Governor, Shalom Salaam, Shoestring, Lovejoy, Love Hurts, Where the Heart Is, A Touch of Frost, Silent Witness, The Mentalist, Dressing for Breakfast, Capital City, The West Wing, Casualty, The Practice, New Tricks, Toast of London, and Midsomer Murders, among other television programmes in Britain and the United States.
A jury at the High Court awarded her £10,000 in damages after Myskow, in an article for the newspaper, had referred to Cornwell as someone unattractive, middle-aged and whose "bum is too big".