Kupperberg entered the comics field from comics fandom, as had his brother, writer/artist Alan Kupperberg. Paul (with Paul Levitz) produced the comics fanzine The Comic Reader between 1971—1973, and Etcetera between 1972-1973.

Comics

Kupperberg has written an estimated 600 comic book stories, primarily at DC, for the Julius Schwartz-edited Superman, Action Comics, Supergirl, and Superboy titles, as well as the new Doom Patrol, Vigilante, Green Lantern, The Brave and the Bold, Showcase, Superman Family, House of Mystery, Weird War Tales, Justice League of America, Ghosts, Star Trek, Aquaman, Adventure Comics, The Savage Sword of Conan, and many others. Kupperberg created the comic book series Arion Lord of Atlantis (1981—1985), Checkmate! (1988—1992), and Takion (1996). He wrote the syndicated Superman newspaper comic strip (with Jose Delbo) from 1981—1985 and the Tom & Jerry newspaper strip from 1990-1991.

Mini-series

Kupperberg wrote the first comic book mini-series, The World of Krypton (1979); his other mini-series include The Phantom Stranger (with Mike Mignola and P. Craig Russell), Power Girl, Peacemaker, Super Powers (with Jack Kirby), and the first comic book adaptation of He-Man and the Masters of the Universe. He has also written movie parodies and humor for Marvel’s Crazy Magazine (1977—1983), the series Trash for Britain’s 2000 AD, with artist Nigel Dobbyn, and The Online Multipath Adventures of Superman web-animation (1998). Most of his current comic book writing appears in the DC-published Cartoon Network licensed comics on such characters as Johnny Bravo, I.M. Weasel, Hi Hi Puffy AmiYumi, and Scooby Doo.

Prose

Kupperberg's prose credits include The Atlas to the DC Universe (Mayfair Games, 1992), The Doom Patrol Sourcebook (Mayfair Games, 1993), and the Spider-Man novels Crime Campaign and Murdermoon (both Pocket Books, 1979). He has had short stories published in the anthologies The Further Adventures of Batman Featuring Catwoman (Bantam Books, 1993), Fear Itself (Warner Books, 1995), Superheroes (Ace Books, 1995, edited by John Varley) and Oceans of Magic (DAW Books, 2001). His adult novel, JSA: Ragnarok, was scheduled to be published in 2006 but has been indefinitely delayed due to the bankruptcy of its publisher, iBooks.

His other published work includes the young adult novel Wishbone Mysteries: The Sirian Conspiracy (co-written with Michael Jan Friedman, Big Red Chair Books, 1999), as well as color and activity books featuring Firehouse Tales. In 2005, Kupperberg began writing for the weekly satiric and humor tabloid, Weekly World News.

Magazine work

From 1981-1982 Kupperberg was assistant editor on Video Action Magazine, one of the first newsstand magazines to focus on the then burgeoning home video market. He also wrote numerous articles for the magazine. Among his other non-fiction work are many introductions and historic prefaces to various DC collected editions and Archives ('The Essential Showcase', The Flash Archives Volume 1, Action Comics Archives Volume 2, etc.), as well as essays for the anthology You Did What?: Mad Plans And Great Historical Disasters (Harper Paperbacks, 2004). Since 2003, Kupperberg has written numerous non-fiction books for young adults, including: Spy Satellites, The Tragedy Of The Titanic, Astronaut Biographies: John Glenn (a Society Of School Librarians International Honor Book, 2004), Critical Perspectives On The Great Depression, The Nature Of Disease, Edwin Hubble And The Big Bang, The History Of The New York Colony, Rodeo Clowns, Origins Of The Action Heroes: Spider-Man, Cutting Edge Careers In Robotics, and In The News: Hurricanes for Rosen Publishing.

DC Editorial

From 1991-2006, Kupperberg was on staff at DC Comics, editing such DC Universe titles as The Flash, Wonder Woman, Jack Kirby's Fourth World, Impulse, Peter Cannon Thunderbolt and others. He also edited in DC’s Licensed Publishing department, overseeing such titles as MADvertising: A MAD Look at 50 Years of MADison Avenue by David Shayne, Marv Wolfman's novelization of his landmark comics series Crisis On Infinite Earths, a trilogy of Green Lantern novels by Christopher Priest, Mike Baron and Mike Ahn (both novel and trilogy were published by iBooks), and dozens of MAD reprints, kids storybooks, young adult novels and children’s color and activity books based on DC Comics properties.

Currently...

In early 2006, Kupperberg left DC to become senior editor at the Weekly World News. In 2007, he contributed to the Doctor Who short-story collection Destination Prague, and The Avenger Chronicles from Moonstone Books. The Weekly World News ceased publication in August 2007, and in January 2008, Kupperberg became senior editor of WWE KIDS for World Wrestling Entertainment. He is currently freelancing and consulting for DC Comics, Archie Comics, Moonstone Publishing, Stone Arch Books, Bongo Comics, GIT Corp, and others.

He is currently writing two new ongoing series for Archie Comics which will appear beginning in August 2010 in the second issue of Life With Archie: The Married Life, in magazine format. The series continue the Michael Uslan/Stan Goldberg best-selling Archie wedding series, two ongoing series each featuring one of Archie's two possible futures, one married to Betty and another married to Veronica. He is also writing Captain Action Classified, a new quarterly from Moonstone Comics featuring the 1960s adventures of the original Captain Action, as well children's books based on Superman, Batman, and Wonder Woman for Stone Arch Books, and numerous color and activity books based on DreamWorks properties for Dalmatian Press.

Prose Fiction

• Crime Campaign (Pocket Books, 1979)
• Murder Moon (Pocket Books, 1979)
• “Creature of Habit," in The Further Adventures Of Batman: Featuring Catwoman (Bantam Books, 1993)
• “Food for the Beast," in Fear Itself (Warner Books, 1995)
• “Reflected Glory," in Superheroes (Ace Books, 1995)
• Wishbone Mysteries: The Sirian Conspiracy (Big Red Chair Books, 1999)
• “Walk Upon the Waters,” in Oceans of Magic (DAW Books, 2001)
• The Powerpuff Girls: Buttercup’s Terrible Temper Tantrums (Scholastic Books, 2002)
• "Sargasso Sector," in Star Trek Corps Of Engineers: Grand Design (Simon & Schuster, 2007)
• “Strange Attractor,” in Doctor Who, Short Trips: Destination Prague (Big Finish Books, 2007)
• “The Cloud of Doom,” in The Avenger Chronicles (Moonstone Books, 2008)
• “Man Bites Dog,” in Vampires (Moonstone Books, 2009)
• Jewjitsu: The Hebrew Hands Of Fury (Citadel Books, November 2008)
• JSA: Ragnarok Book 1 (of 3) (DC Comics publishing partner, forthcoming)
• Hey, Sophie! (publication TBD)

Non-Fiction

• DC Comics ... introductions and historic forewords for collected editions of classic comic books, including Action Comics Archive Vol. 2, The Flash Archives Vol. 1, Challengers of The Unknown Archives Vol. 1, Superman: Whatever Happened To The Man Of Tomorrow?, The Essential Showcase, The Doom Patrol Archives Col. 3, Superman: The World Of Krypton, and Superman: The Bottle City Of Kandor.
• Spy Satellites (Rosen Publishing, 2003)
• The Tragedy of the Titanic (Rosen Publishing, 2003)
• You Did What?: Mad Plans and Great Historical Disasters (Harper Paperbacks, 2004)
• Astronaut Biographies: John Glenn (Rosen Publishing, 2004 ... Society of School Librarians International Honor Book, 2004)
• Critical Perspectives On The Great Depression (Rosen Publishing, 2005)
• The Nature of Disease (Rosen Publishing, 2005)
• Edwin Hubble and the Big Bang (Rosen Publishing, 2005)
• The History of the New York Colony Rosen Publishing, 2005)
• Rodeo Clowns (Rosen Publishing, 2006)
• Origins of the Action Heroes: Spider-Man (Rosen Publishing, 2006)
• Cutting Edge Careers in Robotics (Rosen Publishing, 2007)
• In the News: Hurricanes (Rosen Publishing, 2007)
• Great Historic Disasters: The Influenza Pandemic of 1918-1919 (Facts On File, 2008)
• Building America, Then and Now: The Alaska Highway (Facts On File, 2008)

Comic books and syndicated newspaper strips

• Over 600 stories featuring Batman, Justice League of America, Green Lantern, Aquaman, Star Trek, Jimmy Olsen, He-Man and The Masters of the Universe, Peacemaker, The Phantom Stranger, Power Girl, Green Arrow, Super Powers, Captain America, Conan The Barbarian, The Simpsons, Cartoon Network Characters (including Scooby Doo, Johnny Bravo, The Grim Adventures of Billy & Mandy, Ed, Edd & Eddy, and I.M. Weasel)
• The World’s Greatest Superheroes Presents Superman (Tribune Company, 1981—1985)
• Superman ... Superman, Action Comics, and DC Comics Presents (DC Comics, 1980—1985)
• Arion, Lord of Atlantis ... creator and writer (DC Comics, 1981—1985)
• Superboy (DC Comics, 1982—1985)
• Supergirl (DC Comics, 1982—1985)
• Vigilante (DC Comics, 1984—1988)
• The New Doom Patrol ... creator and writer (DC Comics, 1987—1989)
• Checkmate! ... creator and writer (DC Comics, 1988—1992)
• Tom & Jerry ... syndicated newspaper strip (Editors Press Service, 1990—1991)
• Trash ... creator and writer, (in 2000 AD, 1991—1992)
• Takion ... creator and writer (DC Comics, 1996)
• The Multi-Path Adventures of Superman: Bizarro ... 6-part animated series for the Internet (BDE, 1998)

Micellaneous

• Specialty advertising and custom comic books for clients including Radio Shack, Power Tool Institute, Bariatric Health Institute, Silly Putty, Mattel Toys, Fruit-of-the-Loom, NASCAR, Schering-Plough Pharmaceutical
• Role playing game manuals for Mayfair Games
• Color and activity books for Scholastic, Simon Scribbles (Simon & Schuster), Dalmatian Publishing, Meredith Books

Magazines

• Video Action Magazine ... Various articles on topics including emerging video technology, hardware, legal issues and reviews (1980—1981)
• Crazy Magazine ... Movie parodies and humor articles (Marvel Comics, 1977—1983)
• Weekly World News ... Satiric and humorous articles on politics and social issues for weekly tabloid
• WWE Kids Magazine ... Wrote articles, comic strips and features for World Wrestling Entertainment’s magazine for children (2008)