Giffen was born in Queens, New York City.
He is best-known for his long runs illustrating and later writing the futuristic superhero team book Legion of Super-Heroes in the 1980s and 1990s, and for co-creating the humorous, international version of the Justice League in the late 1980s (which he later revisited in "Formerly Known as The Justice League", calling them The Super Buddies). He also created the alien mercenary Lobo (with Roger Slifer), and the irreverent "want-to-be" hero, Ambush Bug.
Giffen's first published work was "The Sword and The Star", a black and white series with writer Bill Mantlo. He has worked on titles (owned by several different companies) including Woodgod, All Star Comics, Doctor Fate, Drax the Destroyer, Heckler, Nick Fury's Howling Commandos, Reign of the Zodiac, Suicide Squad, Trencher (to be re-released in a collected edition by Boom! Studios.), T.H.U.N.D.E.R. Agents, and Vext. He was also responsible for the English adaptation of the Battle Royale and Ikki Tousen manga, as well as creating "I Luv Halloween" for Tokyopop. He also worked for Dark Horse from 1994-95 on their Comics Greatest World/Dark Horse Heroes line, as the writer of two short lived series, Division 13 and co-author, with Lovern Kindzierski, of Agents of Law.
He took a break from the comic industry for several years, working on storyboards for television and film, including shows such as The Real Ghostbusters and Ed, Edd 'n' Eddy.
He and his Justice League cohorts (J.M. DeMatteis and Kevin Maguire) have recently unleashed their particular brand of storytelling on a title that he drew in the 1970s, Marvel Comics' The Defenders. The same trio produced more superhero humor in the 3-issue mini-series Hero Squared for Boom! Studios, and the 2-issue mini-series Planetary Brigade.
Keith Giffen was the breakdown artist on the DC Comic book 52, a weekly series following in the wake of the Infinite Crisis crossover (written by Geoff Johns, Greg Rucka, Mark Waid and Grant Morrison). He continued in that role with the follow-up weekly series Countdown (DC Comics). He is also the lead writer for Marvel comics's Annihilation event, having written the one-shot prologue, the lead-in stories in Thanos and Drax, the Silver Surfer as well as the main six issues mini-series.
Giffen remains a prolific creator of independent comics. Between 2005 and 2007 he's co-created and often authored or co-authored such books as 10, Tag and Hero Squared for Boom! Studios for Zapt! and I Luv Halloween for TOKYOPOP, Common Foe and Tabula Rasa for Desperado Publishing/Image Comics and Grunts for Arcana. Many of these were co-authored with his frequent collaborator Shannon Denton.
Giffen's art has taken on many styles over the years. His early work tended towards a heavy influence from Jack Kirby. After an early stint at Marvel, he began doing layouts for artist Wally Wood during the late 1970s revival of the Justice Society of America.
When he returned to comics after a hiatus, his style was more precise and reminiscent of George Perez and Jim Starlin and helped make Legion of Super-Heroes DC's second most popular comic after George Perez's New Teen Titans. It was his work on the Legion that rocketed him to comic book artist fame and gave him a creative control with the national companies that few artists achieved. He peppered his artwork with in-jokes such as upside down Superman logos, hidden Marvel characters, and eyeball creatures, and created an alternate futuristic alphabet in which he scrawled humorous messages on signs in the background of his panels.
As his style loosened up, he found himself drawn to the work of José Muñoz.
Soon thereafter he developed a scratchier, more impressionistic style, using a highly stlylized method of drawing directly with ink on titles such as Trencher and Lobo.
After his lengthy sabbatical from comics work, Giffen returned with a style that some said was influenced by his Justice League artist Kevin Maguire that was mid-way between the tight, controlled pencils of his early Legion days and the freer but less anatomically correct style he had later adopted.
For many years, Giffen would co-write comics, but only as a plotter. He relied on others such as Robert Loren Fleming to supply dialogue, even when he was basically the author of the work. He co-wrote the Freak Force series with Erik Larsen, and also co-wrote two Superpatriot mini-series. Beginning with Trencher, Giffen started writing comics fully by himself, although he still collaborates when the project calls for it.
Giffen is known for having an unorthodox writing style, often using characters in ways not seen before. His dialogue is usually characterized by a biting wit that is seen as much less zany than dialogue provided by longtime collaborators DeMatteis and Robert Loren Fleming. That approach has brought him both criticism and admiration, as perhaps best illustrated by the mixed (although commercially rather successful) response to his work in DC Comics' Justice League International. His work on the 2001 version of Suicide Squad was not nearly as successful, however, and his loose, largely satirical style is arguably a detriment to both the English version of the Battle Royale manga and to the third version of the Defenders, published in 2005-2006.
Giffen is known for his humorous takes on existing characters, often focusing on their personality clashes. He also has a tendency to poke fun at trends in comic books or character archetypes. His Ambush Bug miniseries is especially noted for its in-jokes such as Villian the Villain, Cheeks the Toy Wonder, and the use of DC editor Julius Schwartz as a character.
He is also known for sudden plot twists and abrupt often tragic turns of fate. During his late 1980s-early 1990s run on the Legion of Super-Heroes light comical issues were often followed by darker ones where popular characters were maimed or killed.
n February of 1986 Mark Burbey published "The Trouble With Keith Giffen" in The Comics Journal #105, an examination of recent dramatic changes in Keith Giffen's drawing style. Giffen, Burbey pointed out, had changed from a slick, clean Jim Starlin style to an avant garde, heavily inked one. However, critics and fans largely agreed that this new style suited the strange and funny projects in which was involved.
In the article, Burbey displayed several panels side by side to illustrate his allegation that Giffen was copying, or "swiping" the work of Jose Muñoz. In response, Giffen parodied himself by alluding to the controversy by drawing Ambush Bug with the appearance of Snoopy in Son of Ambush Bug #5. Robert Loren Fleming wrote the panels for it.
Loyal Giffen fans defended him by arguing that Giffen had actually ghosted the Munoz work, with some of the most extreme maintaining that in fact Munoz was simply a Giffen pseudonym, prompting two different men, each claiming to be Munoz, to launch competing defamation lawsuits against both Giffen and his fans (James Branch, "Who Knows Munoz?", The Comic Book Companion, March 1987).
However, Giffen himself acknowledges Munoz' influence, referring to the incident by saying: "I had a bad incident with studying somebody's work very closely at one point and I resolved never, ever to do it again. I can get so immersed in somebody's work that I start turning into a Xerox machine and it's not good.... There was no time I was sitting there tracing or copying, no. Duplicating, pulling out of memory and putting down on paper after intense study, absolutely" (Keith Giffen Interview, Interviewed by Jon B. Cooke, Jack Kirby Collector #29).
At this point in his career, Giffen was considered one of the most popular comic book artists in the industry, along with artists such as John Byrne, George Perez, and Frank Miller. The ensuing controversy hurt Giffen's reputation with those who knew about it.
Although comic book artists such as Byrne and Rich Buckler have engaged in swiping with the knowledge of the comic book publishers, their swiping usually involved copying panels from artwork previously published, and owned, by their publisher. Giffen allegedly swiped from work for which the publisher did not have the copyright.
However, DC Comics loyally protected him. They removed him as prime artist on his run of DC titles, such as Ambush Bug, and gave him full-time writing duties on Justice League until the controversy was largely forgotten and a new generation of comic book fans came to discover his work. He returned to drawing full time two years later while continuing to plot the Justice League and its numerous spin-offs.
This period also marked Ambush Bug's end as a growing and popular major character at DC. According to Giffen, it had to do with editorial discomfort with the series' humorous approach to the DC Universe: "DC was just too uncomfortable with the (admittedly nicely selling) bully pulpit they'd provided the loose cannons on the creative team".