His first appearances in his two most famous roles were in Terence Fisher's films The Curse of Frankenstein (1957) and Dracula (1958). Cushing will always be associated with playing Victor Frankenstein and Van Helsing in a long string of horror films produced by Hammer Horror. These provided him with 20 years of steady employment despite being of often middling quality. Although talented as an actor, he admitted that career decisions for him meant choosing roles where he knew the audience would accept him. "Who wants to see me as 'Hamlet'? Very few. But millions want to see me as Frankenstein so that's the one I do." He also said "If I played Hamlet, they'd call it a horror film."
A shade under 6' tall and wiry, with a mane of increasingly iron-grey hair and an unemotional, meticulous delivery, he had an energetic onscreen presence. He often performed his own stunts.
Cushing was often cast opposite the actor Christopher Lee, with whom he became best friends. "People look at me as if I were some sort of monster, but I can't think why. In my macabre pictures, I have either been a monster-maker or a monster-destroyer, but never a monster. Actually, I'm a gentle fellow. Never harmed a fly. I love animals, and when I'm in the country I'm a keen bird-watcher," he said in an interview published in ABC Film Review in November 1964.
In the mid-1960s, he played the eccentric Dr. Who in two movies (Dr. Who and the Daleks and Daleks — Invasion Earth 2150 AD) based on the television series Doctor Who. He made a conscious decision to play the part as a lovable, avuncular figure, as a conscious effort to escape from his perceived image as a "horror" actor. "I do get terribly tired with the neighbourhood kids telling me 'My mum says she wouldn't want to meet you in a dark alley'." he said in an interview in 1966. He also appeared in the cult series The Avengers and then again in its successor, The New Avengers. In 1986, he played the role of Colonel William Raymond in 'Biggles'. In Space: 1999, he appeared as a Prospero-like character called Raan.
He was one of many stars to guest on The Morecambe and Wise Show — the standing joke in his case being the idea that he was never paid for his appearance. He would appear, week after week, wearily asking hosts Eric and Ernie, "Have you got my five pounds yet?" (A ludicrously low price for an artists fee, even in the 1970s). When Cushing was the subject of This Is Your Life in 1989, one of the guests was Ernie Wise ... who promptly presented him with a five pound note, but then, with typical dexterity, extorted it back from him. Peter was absolutely delighted with this, and cried: "All these years and I still haven't got my fiver!"
Cushing played Sherlock Holmes many times, starting with Hammer's The Hound of the Baskervilles (1959), the first colour Holmes film. Cushing, who resembled classic Holmes portrayer Basil Rathbone, seemed a natural for the part, and he played the part with great fidelity to the written character -- that of a man who is not always easy to live with or be around -- which had not been done up to that point. He followed this up with a performance in 16 episodes of the BBC series Sir Arthur Conan Doyle's Sherlock Holmes (1968), of which only six episodes survive. Finally, Cushing played the detective in old age, in The Masks of Death (1984) for Channel 4.
Six years later, his feelings were unchanged: "When Helen passed on six years ago I lost the only joy in life that I ever wanted. She was my whole life and without her there is no meaning. I am simply killing time, so to speak, until that wonderful day when we are together again."
In 1986, Cushing appeared on the British TV show Jim'll Fix It. His "wish", "granted" by Jimmy Savile, was to have a strain of rose named after his late wife. Cushing's letter to the show, in copperplate handwriting, was shown, as was the identification and naming of a rose named "Helen Cushing".
Costuming difficulties resulted in a piece of trivia about Star Wars. He was presented with ill-fitting riding boots for the Moff Tarkin role and they pinched his feet so much that he was given permission by George Lucas to play the role wearing his slippers. The camera operators filmed him above the knees or standing behind the table of the conference room set. Also, during filming of Star Wars, a star-struck Carrie Fisher found it hard to deliver her lines to him and seem terrified in the presence of a charming, polished man who smelled of 'linen and lavender' when in their first scene together, her character speaks of Cushing's as having a 'foul stench'.
For Star Wars Episode III: Revenge of the Sith, George Lucas wanted Cushing, now deceased, to reprise his role as Tarkin through the use of archive footage and digital technology, but poor film quality made this impossible. Besides, the scene required a full-body appearance of Tarkin, which was unavailable due to Cushing's use of slippers instead of boots when performing. Instead, Wayne Pygram took the role, though he underwent extensive prosthetic makeup for his brief cameo.
In 1989, Cushing was made an Officer of the Order of the British Empire. He retired to Whitstable, where he had bought a seafront house in 1959, and continued his hobby of birdwatching, and to write two autobiographies. Cushing also worked as a painter, specialising in watercolors, and wrote and illustrated a children's book of Lewis Carroll style humor, The Bois Saga.
His final professional engagement was as co-narrator of Flesh and Blood, the Hammer Heritage of Horror, produced by American writer/director Ted Newsom. As co-narrator, Cushing thus took his "last bow" with friend Christopher Lee, the BBC and Hammer Films. The narration was recorded in Canterbury near Cushing's home. The show was first broadcast in 1994, the week before Cushing's death from cancer in a Canterbury hospice, aged 81.
In an interview on the DVD release of Hound of the Baskervilles, Lee remarked on his friend's death: "I don't want to sound gloomy, but, at some point of your lives, every one of you will notice that you have in your life one person, one friend whom you love and care for very much. That person is so close to you that you are able to share some things only with him. For example, you can call that friend, and from the very first maniacal laugh or some other joke you will know who is at the other end of that line. We used to do that with him so often. And then when that person is gone, there will be nothing like that in your life ever again".
Cushing died of prostate cancer on 11 August 1994 in Canterbury, Kent, England five years after he was made an Officer of the British Empire in recognition of his contributions to the acting profession in Britain and worldwide.