Gary Gianni began his career as an editorial illustrator for Chicago Newspapers. As a courtroom sketch artist for television he covered the trial of serial killer John Gacy. Gary also worked as a book and magazine illustrator. He began to work in the comic book field in 1990. He received the Comic book Eisner Award with writer Archie Goodwin for a batman story in 1997. He also illustrated books by authors ranging from Melville and Stevenson to Robert E. Howard and H.P. Lovecraft. Contemporary authors such as Michael Chabon and Ray Bradbury have had their work illustrated by Gianni as well.
His other comic work includes the Shadow, Tom Strong and Indiana Jones. He is also known for his own occult detective mystery comicbook, Eisner- nominated The MonsterMen.
Beginning in 2004, worked on the syndicated newspaper comic strip Prince Valiant.
More recently, Gianni has worked with George R. R. Martin and produced a Song Of Ice And Fire Calendar as well as illustrations for the author’s novel, A Knight of the Seven Kingdoms.
In 2017, he teamed up with Mike Mignola, and crafted Hellboy’s graphic novel, ”Into The Silent Sea". Currently, he is illustrating another novel, George R. R. Martin’s Fire And Blood.