Koontz was born on July 9, 1945, in Everett, Pennsylvania. He describes his youth as one of poverty under the abuse of a violent, drunk, skirt chasing father. He graduated from Shippensburg University of Pennsylvania in 1967, and soon after went to work as an English teacher at Mechanicsburg High School in Mechanicsburg, Pennsylvania.

In his spare time he wrote his first novel, Star Quest, which was published in 1968. Koontz went on to write over a dozen science fiction novels. Seeing the Catholic faith as a contrast to the chaos in his family, Koontz converted in college because it gave him answers for his life, admiring its "intellectual rigor" and saying it permits a view of life that sees mystery and wonder in all things. He says he sees the Church as English writer and Roman Catholic convert G.K. Chesterton did. Koontz notes that spirituality has always been part of his books, as are grace and our struggle as fallen souls, but he "never get[s] on a soapbox".

In the 1970s, Koontz began to grow a magnum publishing mainstream of suspense and horror fiction, both under his own name and several pseudonyms, sometimes publishing up to eight books a year. Koontz has stated that he began using pen names after several editor convinced him that authors who switched back and forth between different genres invariably fell victim to "negative crossover" (alienating established fans and simultaneously failing to pick up any new ones). Known pseudonyms used by Koontz during his career include Deanna Dwyer, K. R. Dwyer, Aaron Wolfe, David Axton, Brian Coffey, John Hill, Leigh Nichols, Owen West, Richard Paige, Leonard Chris, and Anthony North. Many of Koontz's pseudonymous novels are now available under his real name.

After thirty-five novels, Koontz's acknowledged breakthrough novel was Whispers, published in 1980. The two books before that - The Key to Midnight and The Funhouse also sold over a million copies, but were written under pen names. Thus although Whispers is Koontz's third paperback bestseller, it was the first credited to Koontz. From then on Koontz's books regularly became paperback bestsellers, but his first hardcover bestseller which finally promised some financial stability and lifted him out of the midlist range was his fifty-first book Strangers.Since then, ten hardcovers and thirteen paperbacks written by Koontz have reached #1 on the New York Times Bestseller list.

In 1997, psychologist Katherine Ramsland published an extensive biography of Koontz based on interviews with him and his family. This "psychobiography" (as Ramsland called it) often showed the conception of Koontz's characters and plots from events in his own life.

Early author photos on the back of many of his novels show a balding Koontz with a mustache. After Koontz underwent hair transplantation surgery in the late 1990s, his subsequent books have featured a new clean-shaven appearance with a fuller head of hair. Koontz explained the change by claiming that he was tired of looking like G. Gordon Liddy.

Since 1988 Koontz has contributed almost $73,000 to conservative Republican candidates and causes. He donated to the 2008 US Presidential campaigns of Mitt Romney and John McCain. Newsmeat.com, ? Dean Koontz's Federal Campaign Contribution Report] He and Mrs. Koontz have contributed over $138,000 to Republican candidates for federal office and Republican organizations (1991–2009). In 2005 he supported Governor of California Arnold Schwarzenegger with $5000 in cash donations and more than $100,000 for a fund raising dinner for 123.

Many of his novels are set in Newport Beach, California. As of 2006 he lives there with his wife, Gerda. In 2008 he was the world's sixth most highly paid author, tied with John Grisham at $25 million annually.

One of Dean Koontz's pen names was inspired by his dog, Trixie Koontz, a golden retriever, shown in many of his book-jacket photos. Originally a service dog with Canine Companions for Independence (CCI), a charitable organization that provides service dogs for people with disabilities. Trixie was a gift from CCI in gratitude of the Koontz's substantial donations, totalling $2,500,000 between 1991 and 2004. Koontz was taken with the charity while he was researching his novel Midnight, a book which included a CCI-trained dog, a black Labrador retriever named Moose.In 2004 when Koontz wrote and edited Life Is Good: Lessons in Joyful Living in her name and in 2005, Koontz wrote a second book credited to Trixie, Christmas Is Good. Both books are written from a supposed canine perspective on the joys of life. The royalties of the books were donated to Canine Companions for Independence. In 2007, Trixie contracted terminal cancer creating a tumor in her heart. The Koontzes had her put to sleep outside of their family home on June 30. After Trixie's death, Koontz has continued writing on his website under Trixie's names, in "TOTOS", standing for Trixie on the Other Side.It is widely thought that Trixie was his inspiration for his November 2007 book The Darkest Evening of the Year, about a woman who runs a golden retriever rescue home, and who rescues a 'special' dog, named Nickie, who eventually saves her life. In August 2009, Dean published "A Big Little Life," a memoir of his life with Trixie.

In October 2008 Koontz released he had adopted a new dog, Anna. It was eventually learned that Anna was the grandniece of Trixie.

Characters

• art dealer and professional thief (Tucker appeared in the novels Blood Risk, Surrounded, and The Wall of Masks, all written under the pseudonym Brian Coffey); and the (as yet unfinished) Moonlight Bay Trilogy, whose hero, Christopher Snow, appears in the novels Fear Nothing and Seize the Night (a proposed third entry, Ride the Storm, has yet to appear). In recent years, however, Koontz has written four novels featuring the character of Odd Thomas (Odd Thomas, Forever Odd, Brother Odd, and Odd Hours), as well as the ongoing Dean Koontz's Frankenstein series, based on a concept for a failed television series that Koontz was briefly involved with. The show's pilot episode wound up being repackaged as a direct-to-DVD movie. Additionally, the Christopher Snow novels are loosely connected to Watchers, and the Tranquility Motel of Strangers appears in the Odd Passenger web series. Odd Thomas also had a link to the Christopher Snow series via a sweatshirt with the words "mystery Train." Deucalion of the Frankenstein series made an appearance at St. Bart's monastery which was the backdrop for Brother Odd.
• The female lead is often intelligent, beautiful, witty, and assertive, and is just as often paired with a more sensitive and easygoing male counterpart (e.g., Bobby and Julie Dakota in The Bad Place, Detectives Michael Madison and Carson O'Conner in Dean Koontz's Frankenstein, Tommy and Del in Ticktock, and Jimmy and Lorrie Tock in Life Expectancy, and Odd and Stormy in Odd Thomas, to name a few).
• Several of Koontz's female protagonists are single mothers bringing up their children against all the odds.
• Male protagonists are usually tough and capable, often either police officers (as in Phantoms, Dragon Tears, or The Door to December) or seemingly mild mannered sorts who are revealed to have police or military experience in their background (as in The Good Guy, Dark Rivers of the Heart, The Eyes of Darkness, Watchers, Shadow Fires, and others).
• Many of Koontz's heroes come from abusive (or at least dysfunctional) backgrounds, but are nonetheless portrayed as successful, financially independent, strong-willed, and emotionally stable.
• Conversely, his antagonists are often sociopath monsters with no redeeming or humanizing qualities whatsoever, who are invariably destroyed by the story's end; many of Koontz's villains are delusional, and consider their extremely warped and elaborate worldviews to be philosophically transcendent (e.g., Edgler Vess from Intensity, Corky Laputa from The Face, Vassago from Hideaway, Bryan Drackman from Dragon Tears, Vince Nasco from Watchers, Preston Maddoc from One Door Away from Heaven, Valis in Velocity, Thomas Shaddack in Midnight, Junior Cain in From the Corner of His Eye, and Krait in The Good Guy).
• Many of Koontz's novels feature sympathetic portrayals of characters who suffer from some mental or physical abnormality (e.g., Christopher Snow from the Moonlight Bay Trilogy, Regina from Hideaway, Shepherd in By the Light of the Moon, Thomas in The Bad Place, and Harry in Midnight, which smoothly combines with Koontz's common theme of dogs, as portrayed by Harry's helpful service dog who also provides him with friendship).
• Koontz is an only child, and many of the protagonists in his stories are only children (e.g. Christopher Snow, Odd Thomas, Jimmy Tock - although born a twin, he was raised an only child - from Life Expectancy, Laura Shane from Lightning, Fric from The Face).

Plot

• Though Koontz's books often feature fantastical plot elements, he usually offers plausible, logically consistent science-based explanations for these bizarre events. Very few of Koontz's novels involve the overtly supernatural, instead often relying on unique genetic traits and natal conditions.
• Koontz's protagonists often arm themselves with guns to combat the various monsters and madmen they are forced to do battle with. Often a Chief's Special or Combat Magnum Heckler & Koch P7 appear as handguns (Koontz himself is a lifelong gun owner). An exception to this rule has been the recurring character Odd Thomas who is said in fact to dislike guns due to his childhood trauma of his mother threatening suicide by using her favorite gun, however the fourth book in the series, Odd Hours seems to ignore this established trait.
• A protagonist having to hide a dead body.
• A desperate struggle for survival that leads to a final confrontation where good completely vanquishes evil, usually leading to a "happy ending" for the main characters.
• A shadowy conspiracy of assassination or illicit and unethical scientific research — or both — involving the police or a government agency, or rogue elements within them.

Themes

• Serious themes about the importance of faith, especially faith in God.
• Duality, such as Mr. Murder or a key point in House of Thunder.
• Characters who follow an unwavering moral compass, but do not conform to organized religion or depend on the law.
• The ideal that love and compassion can save one from the apparent absurdities of existence and the cruelties of life.
• Love for children by their parents.
• Reflection (sometimes at length) on the decline of modern society in the past twenty to thirty years, either in a dialogue between two characters or in the private musings of the protagonist, sometimes centering the blame on liberal-based tolerance of criminal and/or undesirable activity; free love, drug use, and political correctness are frequent targets (the antagonist of Dragon Tears, for instance, evidently owes not only his superhuman abilities but also his pathological personality to his mother's use of illicit drugs while he was in utero).
• A particular high respect for humanity and repugnance for those who degrade any human. Sometimes (as in One Door Away from Heaven) taking a critical stance against "life" issues like Utilitarian bioethics.
• A lack of atonement or redemption from the villains and antagonists, coinciding with main characters who are (eventually) clearly depicted as either good or evil with little moral ambiguity. Little sympathy is elicited for the antagonists. However, two exceptions to this are Watchers and Mr. Murder.
• Scientific themes such as Quantum Theory and Quantum Mechanics have emerged in many of Koontz's novels, providing a new and boundless territory of unique and enigmatic subject matter.

Other trademarks

• Koontz is an avid dog lover, and canines (typically an unusually smart Golden or Labrador Retriever) often feature prominently in his works: Fear Nothing, Seize the Night, The Taking, Watchers, Dark Rivers of the Heart, Dragon Tears, One Door Away from Heaven, Ticktock, Twilight Eyes (Towards the end of the book) and The Darkest Evening of the Year are prime examples. Cats have often fared worse in his books (Koontz is allergic to felines), though he has occasionally included cats as characters, most notably the smart feline Mungojerrie in the Christopher Snow novels, Terrible Chester in the Odd Thomas novels and Aristophanes in The Mask.
• A setting in southern California.
• A Smith and Wesson .38 caliber Chiefs Special or Heckler and Koch P7.
• Use of the words "preternatural", "ozone", "spoor," "susurration" and "blacktop" is prevalent in his books.
• Vivid, detailed descriptions of the settings' architectural and interior design elements, such as beveled glass.
• Street lights being described as "Sodium Vapor lights".
• Amoral scientists using brutalizing techniques (sometimes upon children) to further their research (Sole Survivor, Midnight, Frankenstein, The Door to December, The Eyes of Darkness)
• References to literature and poetry of which Koontz is a fan. The poetry of T. S. Eliot plays a prominent role in The Taking, and many of the same lines by Eliot are seen in Velocity. Fear Nothing includes a character named Tom Eliot, another reference to the famous poet. Little Ozzie from the Odd Thomas series often quotes T.S. Eliot and Shakespeare.
• Plants and flowers are described in hortocultural detail, and bougainvillea flowers often feature in Dean Koontz's books.
• Small references to Japan are often made. Such as plants and characters with a Japanese name, or people having Japanese gardens, furniture or enjoying Japanese food and drink.
• Strange, quirky descriptions, e.g. The Darkest Evening of the Year "...but a pair of lamps shed light as lusterless as ashes and the colors were muted as though settled smoke from a long-quenched fire had laid a patina on them."
• Frequently references Alice's Adventures in Wonderland.
• Frequent quotations from The Book of Counted Sorrows, a book that Koontz made up. Aside from the quotes, he personally wrote, Koontz wrote one book of poetry, entitled "The Paper Doorway."
• Frequent instances of characters with minor wounds self-administering or being treated with Neosporin.
• Main characters drive a Ford Explorer in several novels.
• Frequently mentions The United States Marine Corps.

Though several of his novels have been adapted either as motion pictures or television movies, Koontz is generally unhappy with most of these adaptations. According to a 1996 interview, Koontz was so unhappy with the final cut of the film adaptation of his novel Hideaway that he now insists on keeping creative control over all subsequent films based on his books.

Film adaptations

• Frankenstein
• The Husband (TBA) — Focus Features Dean Koontz The Husband, The Husband Movie - Dean Koontz - The Official Site
• Frankenstein (2004) — USA Network - starring Adam Goldberg, Parker Posey, Michael Madsen, Vincent Perez, and Thomas Kretschmann (Koontz pulled out of the project midway through production because he did not like the direction the film was headed. He ended up writing his own books with the storyline he had originally created. The project continued without him.) Dean Koontz Website, Suspense Novel - Dean Koontz - The Official Site
• Black River (2001) — Fox - starring Jay Mohr, and Stephen Tobolowsky
• Sole Survivor (2000) — Fox - starring Billy Zane, John C. McGinley, and Gloria Reuben
• Watchers Reborn (1998) — Concorde Pictures - starring Mark Hamill
• Phantoms (1998) — Miramax/Dimension Films - starring Peter O'Toole, Ben Affleck, Rose McGowan, and Joanna Going.
• Mr. Murder (1998) — ABC—starring Stephen Baldwin, Thomas Haden Church, and James Coburn
• Intensity (1997) — Fox—starring John C. McGinley, Molly Parker, and Piper Laurie
• Hideaway (1995) — Tristar Pictures—starring Jeff Goldblum, Christine Lahti, Jeremy Sisto, and Alicia Silverstone
• Watchers 3 (1994) — Concorde Pictures - starring Wings Hauser
• The Servants of Twilight (1991) — Trimark—starring Bruce Greenwood
• The Face of Fear (1990) — CBS—starring Pam Dawber and Lee Horsley. Also includes Kevin Conroy.
• Watchers II (1990) — Concorde Pictures - starring Marc Singer and Tracy Scoggins
• Whispers (1990) — Cinepix—starring Victoria Tennant, Chris Sarandon, and Jean LeClere
• Watchers (1988) — Universal Pictures - starring Corey Haim, Barbara Williams, and Michael Ironside
• The Intruder (1977) — MGM - starring Jean-Louis Trintignant (French film adaptation of Koontz's novel Shattered)
• Demon Seed (1977) — MGM - starring Julie Christie, Fritz Weaver, and Robert Vaughn as the voice of Proteus