Before serving in World War I, Mortensen graduated from East Side High School in Salt Lake City. He then served as Private in Company D of the 13th Regiment of the United States Infantry from August 6, 1918 to May 16, 1919. At his enlistment, he recorded his occupation as painting.
In May 1920 he traveled in Greece, Italy, Egypt and Constantinople to "sketch for educational purposes." He returned to Utah, then traveled to Hollywood as an escort for his friend's sister, Fay Wray. After two years at the Art Students League he was declared to have "no talent for drawing." Undeterred by this verdict he borrowed money and took off for Greece, to make etchings of the monuments of ancient Attica.
Mortensen was a very self-critical man who began his photographic career taking portraits of Hollywood actors and film stills. During the 1920s and 1930s, he was inspired by horror films being adapted in studios, and ended up making portraits about them in his own style. His favorite photographic topics were of witches, dancers, demons, peasants, and Shakespearean actors.
In 1931 he moved to the artist community of Laguna Beach, California, where he opened a studio and the William Mortensen School of Photography.
Using pens, paints, pumice and razor blades, he preferred the Pictorialist style of manipulating photographs to produce romanticist painting-like effects. Mortensen's style of art consisted of him using a bromoil process. The style brought him criticism from straight photographers of the modern realist movement and, in particular, he carried on a prolonged written debate with Ansel Adams in the pages of Camera Craft magazine.
His arguments defending romanticist photography led him to be "ostracized from most authoritative canons of photographic history." In an essay, Larry Lytle wrote, "Due to his approach—both technically and philosophically in opposition to straight or purist adherents — he is amongst the most problematic figures in photography in the twentieth-century... historians and critics have described his images as "...anecdotal, highly sentimental, mildly erotic hand-colored prints...", "...bowdlerized versions of garage calendar pin-ups and sadomasochist entertainments...", "...contrived set-ups and sappy facial expressions...", and Ansel Adams variously referred to Mortensen as the "Devil", and "the anti-Christ." In addition, the more realistic photojournalism emerging from World War II correspondents, and carried in national newsmagazines, caused Mortensen's more posed and contrived photos to fade from the public mind. He was largely forgotten by the time of his death in 1965.
Recent years have brought praise for Mortensen's development of manipulation techniques and a renewed interest in his work. In 2013, one of Mortenson's students, portrait photographer Robert Balcomb, published a book — Me and Mortensen — about his time studying with Mortensen in Laguna Beach.
He wrote nine books about technique in photography in conjunction with George Dunham.
In order of original publication date except where noted.
- —— (1934). Projection Control. San Francisco, CA, USA: Camera Craft Pub. Co. hdl:2027/mdp.39015033402630. OCLC 567991261.
- —— (1973) . Monsters and Madonnas. San Francisco, CA, USA: Camera Craft Pub. Co. ISBN 9780405049279. OCLC 643549864, 643549864.
- —— (1935). Pictorial Lighting. OCLC 42857350.
- —— (1937). The Command to Look: A Formula for Picture Success. San Francisco, CA, USA: Camera Craft Pub. Co. OCLC 872528013.
- —— (1937). The Model: a Book on the Problems of Posing. San Francisco, CA, USA: Camera Craft Pub. Co. OCLC 833593606.
- —— (1938). Print Finishing. San Francisco, CA, USA: Camera Craft Pub. Co. OCLC 763128067.
- Republished —— (2012). Print Finishing. Literary Licensing, LLC. ISBN 9781258401436.
- —— (1940). Outdoor Portraiture: Problems of Face and Figure in Natural Environment. San Francisco, CA, USA: Camera Craft Pub. Co. OCLC 768060028.
- —— (1940). Mortensen on the Negative. New York, NY: Simon & Schuster. OCLC 568026105.
- ——; Paul, Don M (1941). Flash in Modern Photography. San Francisco, CA, USA: Camera Craft Pub. Co. OCLC 567982784.
- —— (1942). The New Projection Control. San Francisco, CA, USA: Camera Craft Pub. Co. OCLC 567991275.
- —— (1954). The Texture Screen. Newport Beach, CA, USA: Jay Curtis Publications. OCLC 70854143.
- —— (1954). The Female Figure: Flesh and Symbol. Mortensen series. Newport Beach, CA, USA: Jay Curtis Publications. OCLC 70853997.
- —— (1954). The Paper Negative. Mortensen series. Newport Beach, CA, USA: Jay Curtis Publications. OCLC 70853857.
- —— (1954). Know Your Negative. Mortensen series. Newport Beach, CA, USA: Jay Curtis Publications. OCLC 70900120.
- ——; Dunham, George (1956). How to Pose the Model. San Francisco, CA, USA: Camera Craft Pub. Co. OCLC 500685587.
- —— (1927). The King of Kings: as portrayed by photographic reproductions of scenes and characters from the motion picture. Based on the gospels of Matthew, Mark, Luke and John; produced by Cecil B. DeMille. OCLC 12033875.
- ——; Mortensen, Myrdith (1971). The Mortensen Collection of the Photographic Society of America. San Francisco, CA, USA: Camera Craft Pub. Co. OCLC 70861915.
- ——; Los Angeles Center for Photographic Studies (1971). The Photographic Magic of William Mortensen. Los Angeles, CA, USA: Los Angeles Center for Photographic Studies. OCLC 6014461.
- Dawson, Michael; Dillon, Diane; Coleman, A.D.; Lytle, Larry; Rule, Amy (1998). William Mortensen : A Revival. The Archive (University of Arizona. Center for Creative Photography). Tucson, AZ: University of Arizona Center for Creative Photography. ISBN 9780938262336. OCLC 39818931.
- ——; Lytle, Larry; Moynihan, Michael; Coleman, A.D. (2014). American Grotesque: The Life and Art of William Mortensen. Port Townsend, WA: Feral House. ISBN 9781936239979. OCLC 875240443.
- Soltys, Richard J.; Stone, Earl (c. 1963). Monsters and Madonnas: the World of William Mortensen (documentary film). Narrated by Vincent Price.
- Jones, Robert (May 23, 2003). "William Mortensen: A Revival: The Strange Case of William Mortensen". photo.net. Waltham, MA, US: NameMedia, Inc. Retrieved January 24, 2015.
- Gillette, J Stephen (1997). "The life and times of William Herbert Mortensen: United States, 1897-1965". PSA Journal. Photographic Society of America. 63 (6): 16. ISSN 0030-8277.
- Adjutant General's Office of the War Department. Military service cards, c. 1898 – 1975. Series: 85268, Reel: 27. Salt Lake City, UT: Utah Department of Administrative Services. Division of Archives and Records Service. OCLC 793096427. See Inventory of Military service cards from Department of Administrative Services. Division Archives and Records Service, i ca. 1898-1975.
- National Archives and Records Administration (NARA) (January 2, 1925 – March 31, 1925). Passport Applications. Washington, DC. OCLC 866104303.
- Wray, Fay (1989). On The Other Hand: A Life Story. New York, NY: St. Martin's Press. pp. 27–98. ISBN 9780312022655. OCLC 17917980.
- Peres, Michael R. (April 25, 2007). Focal encyclopedia of photography: digital imaging, theory and applications (4th ed.). Amsterdam; London: Focal Press. p. 277. ISBN 9780240807409. OCLC 499055803.
- Warren, Lynne (2006) . "Group F/64". Encyclopedia of Twentieth-Century Photography. Taylor and Francis. pp. 637–642. ISBN 9780203943380. OCLC 190846013.
- Lytle, Larry (April 23, 2010). "THE COMMAND TO LOOK: The Story of William Mortensen, Part I". thescreamonline.com. Retrieved January 29, 2015.
- Lovejoy, Bess (December 4, 2014). "The Photographer Who Ansel Adams Called The Anti-Christ". Arts & Culture. smithsonianmag.com. Washington, DC: Smithsonian. Retrieved January 29, 2015.
- Lytle, Larry (April 15, 2010). "THE COMMAND TO LOOK: The Story of William Mortensen, Part III". thescreamonline.com. Retrieved January 29, 2015.
- "Hood Medal". rps.org. Bath, UK: Royal Photographic Society. Retrieved January 29, 2015.
- "William Mortensen (The Photography Page)". Thescreamonline.com. Retrieved January 31, 2015.
- Stephen Romano Gallery (2014). "'WILLIAM MORTENSEN: AMERICAN GROTESQUE' exhibition". Shishigami.com (Press release). Retrieved January 31, 2015. Includes links to reviews, essays, a documentary, and a PDF of Monsters & Madonnas.
- Stephen Romano Gallery (2014). "www.whmortensen.com/". Retrieved January 31, 2015. Contains links to PDFs of The Command To Look and A Pictorial Compendium of Witchcraft; WILLIAM MORTENSEN 1897 - 1965, published by Stephen Romano Gallery (2014).
- William Mortensen at Find a Grave
- "George Eastman House William Mortensen Series". geh.org. Rochester, NY: George Eastman House. 2002. Retrieved January 31, 2015.
- Balcomb, Robert (2013). "CHAPTER II • AND MORTENSEN •". Me and Mortensen: Photography with the Master. Venice, CA, USA: Amphora Editions. ISBN 9780983655008. OCLC 852432429. Retrieved January 31, 2015.
- Pridemore, Heather (2010). The Command to Look: The Nudes of William Mortensen (MA). Ryerson University. OCLC 697300610. Retrieved June 18, 2019. This contains discussion and examples of his nude photography.