In the early 1970s, Peterson moved to Italy and became lead singer of the Italian rock bands Latins 80 and The Snails. Introduced to film director Federico Fellini by the producer of a documentary on Las Vegas showgirls in which she had appeared, she landed a small part in the film Roma (1972). Back in the United States, she toured nightclubs and discos around the country with a musical/comedy act, Mammas Boys. In 1979, she joined the Los Angeles-based improvisational troupe The Groundlings, where she created a Valley girl-type character upon whom the Elvira persona is largely based.

Peterson auditioned for the role of Ginger Grant for the third Gilligan’s Island television movie in 1981, shortly before KHJ-TV offered her the horror host position. Peterson also was a personality on Los Angeles radio station KROQ-FM 106.7 from 1982 to 1983.

She married musician Mark Pierson in 1981. Pierson would soon become her personal manager. They had one daughter, Sadie Pierson (born October 12, 1994), and were divorced on February 14, 2003.

In 1985, Elvira began hosting a home video series called ThrillerVideo, a division of International Video Entertainment (IVE). Many of these films were hand-selected by Peterson. Choosing to stay away from the more explicit cannibal, slasher and zombie films of the time, these were generally tamer films such as The Monster Club and Dan Curtis television films, as well as many episodes of the Hammer House of Horror television series. Since she had refused to host Make Them Die Slowly, Seven Doors of Death, and Buried Alive, however, the videos were released on the ThrillerVideo label without Elvira’s appearance as hostess. After this, several extended episodes of the British namesake series Thriller (i.e. The Devil’s Web, A Killer in Every Corner, Murder Motel) were also released without an appearance by Elvira; in some, such as Buried Alive, the cast replaced her.

Peterson has also portrayed non-Elvira roles in many other films, most notably Pee-wee’s Big Adventure in 1985 alongside friend and fellow Groundling Paul Reubens, who starred as his Pee-wee Herman character; Allan Quatermain and the Lost City of Gold, released in 1987, which starred Richard Chamberlain and Sharon Stone; and All About Evil, as a mother named Linda, who says not to go to the old theater to watch scary movies.

Two Elvira-themed pinball machines were produced by Bally/Midway: Elvira and the Party Monsters in 1989 and Scared Stiff in 1996. A third pinball machine has been produced by Stern Pinball and was released in October 2019, titled Elvira’s House of Horrors.

Beginning in 1996, three Elvira novels (authored by Elvira and John Paragon) were published by Berkley Books, Transylvania 90210, Camp Vamp, and The Boy Who Cried Werewolf. Long out-of-print, all three titles were republished and made available as e-books in 2018.

After several years of attempts to make a sequel to Elvira: Mistress of the Dark, Cassandra and her manager and then-husband Mark Pierson decided to finance a second movie. In November 2000, Peterson wrote, again in collaboration with Paragon, and co-produced Elvira’s Haunted Hills. The film was shot in Romania for just under one million dollars. With little budget left for promotion, Cassandra and Mark screened the film at AIDS charity fund raisers across America. For many people in attendance, this was their first opportunity to see the woman behind the Elvira character. On July 5, 2002, Elvira’s Haunted Hills had its official premiere in Hollywood. Elvira arrived at the premiere in her Macabre Mobile. The film would later be screened at the 2003 Cannes Film Festival.

The success of the ThrillerVideo series led to a second video set, Elvira’s Midnight Madness, released through Rhino Home Video. In 2004 a DVD horror-film collection called Elvira’s Box of Horrors was released, marking Elvira’s return to horror-movie hosting after a ten-year absence.

Elvira was also one of the special characters featured in the 2007 PlayStation 3 game Pain.

She also performed on a track called “Zombie Killer” for the band Leslie and the Ly’s, released in February 2008. The music video for the track features Leslie and the Ly’s performing to a sold-out audience of zombies in a fictional venue called “Elvira Stadium”. A 7″ single was released.

In September 2010, Elvira’s Movie Macabre returned to television syndication in the U.S., this time with public domain films. In October 2014, it was revealed that a new series of thirteen episodes had been produced, 13 Nights of Elvira for Hulu. The show began on October 19, 2014, running through to Halloween.

Peterson was born in Manhattan, Kansas. When she was a toddler, she was scalded by boiling water, and required skin grafts to over 35% of her body, spending three months in the hospital. In a 2011 interview, Peterson stated that as a child, she was more fascinated by horror-themed toys while other girls were occupied with Barbie dolls. In elementary school, she watched House on Haunted Hill, which was the first horror film she ever saw. During her teens, Peterson worked as a go-go dancer in a local gay bar.

Elvira appeared in comic books from DC Comics, Eclipse Comics and Claypool Comics. DC published a short-lived series in the mid ’80s titled Elvira’s House of Mystery. Claypool took over the series and in the 1990s distributed a new series, Elvira, Mistress of the Dark, co-branded with and distributed by Eclipse. After Eclipse ceased publication, the series was distributed solely by Claypool. The series was edited and occasionally written by Richard Howell and featured photographic covers with interior stories and art by Kurt Busiek, Dan Spiegle, Jim Mooney, Steve Leialoha, and others. It ran for 166 issues plus two trade paperback collections, Elvira, Mistress of the Dark: Comic Milestones-Comics Format and Elvira, Mistress of the Dark: Double Delights. In 2012 another series, also titled Elvira, Mistress of the Dark, was announced for a 2013 debut to be written by R.H. Stavis and drawn by Jeff Zarnow. The comic book series, to date, has never materialized.

In 2016, Peterson published an Elvira 35th anniversary photographic retrospective she dubbed a “coffin table” book.

On July 18, 2017, it was announced that a new licensing agreement was made with Dynamite Entertainment for a multitude of new Elvira-related merchandise, including a new comic book series, trading cards, posters, lithographs, card games, and board games. Dynamite formally announced that a new comic book series, Elvira: Mistress of the Dark, written by David Avallone and penciled by Dave Acosta, would hit stores in July 2018. Along with a new comic book series, a new line of graphic novels were mentioned.

Elvira stars in Call of Duty: Infinite Warfare “Absolution” released in 2017.

Peterson originally planned to release her autobiography in October 2020. As of the Fall of 2020, possibly as a result of the COVID-19 pandemic, the release date has been pushed back to September 21, 2021.