Johnny Craig studied at the Art Students League of New York. While attending classes, he worked as an assistant to Harry Lampert, co-creator of All-American Comics' Golden Age superhero the Flash. After Lampert was drafted to serve to World War II, All-American editor Sheldon Mayer kept Craig on as art-department assistant, giving him progressively more responsible art duties. Between 1943 and 1945, Craig served in the Merchant Marines and the U.S. Army.
Returning to comics after his discharge, he drew for EC Comics' Moon Girl and for that companies' crime and Western titles beginning in 1947. When he teamed with Al Feldstein, they used the pseudonym F.C. Aljohn. Craig later brought a clean, crisp, naturalistic approach to EC's legendary horror series — The Crypt of Terror, The Vault of Horror and The Haunt of Fear — plus Crime SuspenStories and Two-Fisted Tales. Wally Wood once said Craig drew "the cleanest horror stories you ever saw".
Unlike the majority of EC artists, Craig also scripted. He was responsible for the stories hosted by the Vault Keeper, and also drew that horror host in the framing sequences of stories by other EC illustrators. He eventually concentrated on The Vault of Horror and Crime SuspenStories, doing the lead story in each of these bimonthly titles. A slow and meticulous artist, Craig would take a full month to complete a story, whereas other EC artists typically required a week.
Craig became the editor of The Vault of Horror early in 1954, giving up his work for Crime SuspenStories at that time. Later that year, he created the Vault Keeper's attractive assistant, Drusilla. After the EC horror books came to an end, Craig edited EC's Extra! in 1955, writing and drawing two stories in each bimonthly issue.
Craig's story "...And All Through the House" in Vault of Horror #35 (March 1954) was adapted for the Joan Collins segment of the 1972 omnibus film Tales from the Crypt. Craig's many covers included that of the infamous