Bagley was born in Salt Lake City and raised in Oceanside, California, where his father was mayor and his mother was a school teacher. Always interested in politics, during high school Bagley participated in a PBS interview of Ronald Reagan. As a member of The Church of Jesus Christ of Latter-day Saints (LDS Church), he was a proselyting missionary in the Bolivia La Paz Mission from 1975–77. In 1978 he received his degree in political science, with a history minor, from Brigham Young University (BYU) in Provo, Utah.
Bagley has two sons, Miles and Alec. Will Bagley, Pat's older brother, is an accomplished historian of the western United States and coauthored This is the Place!: A Crossroads of Utah's Past with Pat in 1996.
In October 2009, while reacting to recent statements by Dallin H. Oaks, an LDS Apostle, about gay marriage protesters and religious freedom, Bagley commented that he was "retired" from the church, though not bitter or angry, and considers his LDS life a "good experience" and "in my blood."
In 1977, during a finance class at BYU, Bagley doodled a political cartoon, which he submitted to the student newspaper, The Daily Universe. This became his first published cartoon, which was reprinted in Time Magazine just weeks later. Bagley submitted more cartoons to the Universe and targeted campus issues, such as BYU's requirement for female students to wear dresses. Some believe the attention from his cartoons helped change the policy.
After graduation, Bagley briefly worked as a caricaturist in the nearby Orem Mall, before being hired as the editorial cartoonist at The Salt Lake Tribune, where he still produces a daily cartoon. His cartoons have appeared in The Washington Post, The Guardian of London, The Wall Street Journal, Newsweek, and The Los Angeles Times. Over the years, he has produced more than 6,000 cartoons for the Tribune. He is syndicated in over 450 American newspapers and his work is regularly featured at Daryl Cagle's Political Cartoonists Index (Cagle.com) and in The Best Editorial Cartoons of the Year. Cagle ranks Bagley as the second most popular political cartoonist on his index.
Bagley is also an illustrator and author of independent political cartoons and children's books. His liberal political stance contrasts with the conservative state of Utah, and has influenced several books of political cartoons and humor, including 101 Ways to Survive Four More Years of George W. Bush, Clueless George Goes To War!, Clueless George Is Watching You!, and Clueless George Takes on Liberals!.
Bagley describes himself as a moderate-Republican who became a liberal independent during the presidency of George W. Bush. Bagley often addresses the predominant Utah culture of conservative politics and the LDS Church. Bagley's joking about Jell-O consumption in Utah helped motivate the Utah State Senate to declare in an official 2001 Legislative Resolution that Jell-O is "a favorite snack food of Utah."
For the 2002 Salt Lake Olympics, Bagley designed many popular commemorative pins that poked fun at local themes, including a "Seven Brides for One Brother" pin and a "Crickets Make Me Barf" seagull pin. During the Olympics, Bagley sold out of his Utah-themed pins and many in high demand were sold at inflated prices. After the events had ended, Bagley continued to produce pins as the only recognized "pin artist" in the world.
- In 1992, Bagley received the Wilbur Award for Religious Communication from the Religious Public Relations Council for a cartoon in the April 23, 1991 Tribune. He was the first cartoonist to receive the award, which is given for "outstanding communication of religious values in the news and entertainment media."
- Bagley's 2002 book Dinosaurs of Utah and Dino Destinations was nominated for the Utah Children's Book of the Year.
- In 2006, Bagley was honored by the Utah Headliners Chapter of the Society of Professional Journalists as the best editorial cartoonist in Utah.
- Bagley was dubbed "Best Illustrator" by Salt Lake City Weekly in their 2007 Artys awards, which annually honor the best artistic talent in the city.
- Bagley was the recipient of the 2007 Torch of Freedom Award from the American Civil Liberties Union of Utah.
- Bagley was awarded the 2009 Herblock Prize for editorial cartooning by a unanimous panel of judges, made up of Garry Trudeau, Jules Feiffer and John Sherffius, representing the Herb Block Foundation.
- Mormons: History, Culture, Beliefs: 2004, White Horse Books (ISBN 0974486035)
- If You Were a Girl in the Time of the Nephites: 1989, Deseret Book (ISBN 0875792499)
- If You Were a Boy in the Time of the Nephites: 1989, Deseret Book (ISBN 0875792502)
- I Spy a Nephite: 1991, Deseret Book (ISBN 0875794157), reissued 2000, White Horse Books paperback (ISBN 1566845750)
- A Nephite in the Works: 1992, Deseret Book (ISBN 0875796303)
- Hana, the No-Cow Wife: 1993, Deseret Book (ISBN 0875797148)
- Where Have All the Nephites Gone: 1993, Deseret Book (ISBN 0875797571)
- Peek-A-Boo Magic: 1995, Buckaroo Books (ISBN 1885628005)
- Norman the Nephite's & Larry the Lamanite's Book of Mormon Time Line: 1995, Deseret Book (ISBN 087579906X)
- Showdown at Slickrock: 1995, Buckaroo Books (ISBN 1885628021)
- Norman the Nephite and the A-maze-ing Conference Center: 2000, White Horse Books (ISBN 1566845920)
- Dinosaurs of Utah and Dino Destinations: 2001, White Horse Books (ISBN 1566846013)
- 101 Ways to Survive Four More Years of George W. Bush: 2005, White Horse Books, (ISBN 0974486043)
- Clueless George Goes To War!: 2005, White Horse Books (ISBN 0974486051)
- Clueless George Is Watching You!: 2006, White Horse Books (ISBN 097448606X)
- Clueless George Takes on Liberals!: 2006, White Horse Books (ISBN 0974486078)
- Fist Bump Heard 'Round the World: The 2008 Election in Cartoons: 2008, White Horse Books (ISBN 0980140625)
Social and religious satire
- I am Appalled...: A Collection of Daily Universe Cartoons: 1979, BYU Chapter of the Society of Professional Journalists and Sigma Delta Chi, with Steve Benson
- We Survive World War Three and You Give Us Light Beer?: Life After Megadeath: 1983, Gibbs Smith (ISBN 0879051418)
- Treasures of Half-Truth: 1986, Signature Books (ISBN 0-941214-47-8)
- "Oh My Heck!": A Pretty, Great Cartoon Book: 1988, Signature Books (ISBN 0941214680)
- The Best of Bagley: 20 Years of Cartoons from The Salt Lake Tribune: 1998, Slickrock Books (ISBN 1892936011)
- Welcome to Utah: 2001, White Horse Books (ISBN 1566846080)
- Bagley's Utah Survival Guide: 2008, White Horse Books (ISBN 0980140609)
- Legalizing Adulthood in Utah: 1991, Aspen West, by Tom Barberi
- Sunday of the Living Dead: 1995, Buckaroo Books, by Robert Kirby (ISBN 978-1-885628-49-7)
- Astro-Nuts!: Riddles About Astronauts and the Planets They Love: 1995, Buckaroo Books, by Rick Walton (ISBN 1-885628-12-9)
- Dino-Might: Pre-Hysterical Dinosaur Riddles: 1995, Buckaroo Books, by Rick Walton (ISBN 1-885628-080)
- The Ghost Is Clear!: Riddles about ghosts, vampires, witches, and other creatures: 1995, Buckaroo Books, by Rick Walton (ISBN 1-885628-11-0)
- Wholly Cowboy!: Cowboy, Cow, and Horse Riddles: 1995, Buckaroo Books, by Rick Walton (ISBN 1-885628-07-2)
- Wake Me for the Resurrection: 1996, Buckaroo Books, by Robert Kirby (ISBN 1885628471)
- Norman the Nephite's Church History Time Line: 1996, Deseret Book, by William W. Slaughter (ISBN 1573451959)
- This is the Place!: A Crossroads of Utah's Past: 1996, Buckaroo Books, by Will Bagley (ISBN 1885628250)
- Pat & Kirby Go To Hell: 1997, Slickrock Books, by Robert Kirby (ISBN 1885628463)
- J. Golden Kimball Stories: 1999, White Horse Books, by James N. Kimball (ISBN 1566845491)
- Family Home Screaming: 1999, Slickrock Books, by Robert Kirby (ISBN 1892936089)
- Kirby Soup for the Soul: 2003, White Horse Books, by Robert Kirby (ISBN 0974486027)
- Fit Kids Cookbook: 2004, White Horse Books, by Kate Duffy and Sarah McRedmond (ISBN 097093016X)
- "Pat Bagley". Bill of Rights Celebration. ACLU of Utah. Retrieved 2009-01-12.
- "Award-winning cartoonist keynotes 26th Women's Conference". The Eagle Online (Price, Utah: College of Eastern Utah). March 3, 2005. Retrieved 2009-01-15.
- Bagley, Pat (1986). Treasures of Half-Truth. Salt Lake City, Utah: Signature Books. Back cover.
- "Pat Bagley Bio". 15th Annual Martin Luther King, Jr. Commemoration 2009. Utah Valley University. Retrieved 2009-01-12.
- "Cartoonist Pat Bagley Weighs in on Oaks Controversy". KCPW-FM. Salt Lake City, Utah. October 20, 2009.
- Rogers, Jay Logan (July 19, 2008). "Cartoonist lampoons Bush, Utah culture". The Daily Utah Chronicle (Salt Lake City, Utah: University of Utah). Retrieved 2009-01-15.
- Olsen, Abbey (November 22, 2005). "Political cartoons create a din: The Benson-Bagley duo in the '70s". BYU NewsNet (Provo, Utah: Brigham Young University). Retrieved 2009-01-15.
- Gardner, Alan (November 13, 2007). "Cagle lists most popular cartoonists". The Daily Cartoonist. Retrieved 2009-01-15.
- "Utah Legislature SR0005". Utah State Legislature. Retrieved 2009-01-15.
- Thomson, Candus (February 10, 2002). "Pinning Their Hopes on the Winter Games". Los Angeles Times. pp. D7. Retrieved 2009-01-15.
- "Pat Bagley Takes on Liberals". The King's English Bookshop. 2006. Retrieved 2009-01-15.
- "1992 Wilbur Award for Religious Communication" (PDF). Sunstone (Salt Lake City, Utah: Sunstone Education Foundation) 16 (3): 63. September 1992. Retrieved 2009-01-12.
- "Artys 2007: Readers' Choice". Salt Lake City Weekly (Salt Lake City, Utah). September 13, 2007. Retrieved 2009-01-15.[dead link]
- "2009 Herblock Prize Winner Announced". Editor & Publisher. February 23, 2009. Retrieved 2009-03-03.
- Bagley at Salt Lake Tribune
- "Award-winning cartoonist keynotes 26th Women's Conference", The CEU Eagle (College of Eastern Utah student newspaper), 3 March 2005