- Tim Curry as Dr. Frank-N-Furter, a transvestite scientist
- Susan Sarandon as Janet Weiss, Brad's fiancée
- Barry Bostwick as Brad Majors, Janet's fiancé
- Richard O'Brien as Riff Raff, a hunchbacked handyman and Magenta's brother
- Patricia Quinn as Magenta, a domestic and Riff Raff's sister
- Little Nell as Columbia, a groupie
- Jonathan Adams as Dr. Everett V. Scott, Frank's rival scientist
- Peter Hinwood as Rocky Horror, Frank's creation
- Trevor White is uncredited as Rocky's singing voice
- Meat Loaf as Eddie, a former delivery boy
- Charles Gray as the criminologist, an expert
Jeremy Newson and Hilary Labow play Brad and Janet's newlywed friends Ralph and Betty Hapschatt. The guests at both the Hapschatt wedding and Frank's convention consist of Perry Bedden, Christopher Biggins, Gaye Brown, Ishaq Bux, Stephen Calcutt, Hugh Cecil, Imogen Claire, Tony Cowan, Sadie Corré, Fran Fullenwider, Lindsay Ingram, Peggy Ledger, Annabel Leventon, Anthony Milner, Pamela Obermeyer, Tony Then, Kimi Wong, and Henry Woolf, as well as an uncredited Rufus Collins.
