Steranko was born in Reading, Pennsylvania. According to Steranko's authorized biography, his grandparents emigrated from Ukraine to settle in the anthracite coal-mining region of eastern Pennsylvania. Steranko's father, one of nine siblings, began working in the mines at age 10, and as an adult became a tinsmith. Steranko later said his father and uncles "would bootleg coal - they would go up into a mountain and open up a shaft.

During the day, Steranko made his living as an artist for a printing company in his hometown of Reading, designing and drawing pamphlets and flyers for local dance clubs and the like. He moved on after five years to join an advertising agency, where he designed ads and drew products ranging from "baby carriages to beer cans". Interested in writing and drawing for comic books, he visited DC Comics as a fan and was treated to a tour of the office by editor Julius Schwartz, who gave Steranko a copy of a script featuring the science-fiction adventurer Adam Strange. Steranko recalled in 2003, "It was the first full script I'd ever seen, complete with panel descriptions and dialogue. I learned a lot from it and eventually went on to create a few comics of my own."  He initially entered the comics industry in 1957, not long out of high school, working for a short time inking pencil art by Vince Colletta and Matt Baker in Colletta's New York City studio before returning to Reading. In 1966, he landed assignments at Harvey Comics under editor Joe Simon, who as one writer described was "trying to create a line of super heroes within a publishing company that had specialized in anthropomorphic animals." Here Steranko created and wrote the characters Spyman, Magicmaster and the Gladiator for the company's short-lived superhero line, Harvey Thriller. His first published comics art came in Spyman #1 (Sept. 1966), for which he wrote the 20-page story "The Birth of a Hero" and penciled the first page, which included a diagram of a robotic hand that was reprinted as an inset on artist George Tuska's cover.  Steranko also approached Marvel Comics in 1966. He met with editor Stan Lee, who had Steranko ink a two-page Jack Kirby sample of typical art for the superspy feature "Nick Fury Agent of S.H.I.E.L.D.". Steranko self-published it in 1970 in the limited-edition "Steranko Portfolio One"; it appeared again 30 years later in slightly altered form in the 2000 trade-paperback collection Nick Fury, Agent of S.H.I.E.L.D. This led to Lee's assigning him the Nick Fury feature in Strange Tales, a "split book" that shared each issue with another feature. Future Marvel editor-in-chief Roy Thomas, then a staff writer, recalled,  [H]e came up to the office ... and I was sent out by Sol [Brodsky] to look at his work and basically brush him off. Stan was busy and didn't want to be bothered that day. But when I saw Jim's work, ... on an impulse I took it in to Sol and said, 'I think Stan should see this'. Sol agreed, and took it in to Stan. Stan brought Steranko into his office, and Jim left with the 'S.H.I.E.L.D.' assignment. ... I think Jim's legacy to Marvel was demonstrating that there were ways in which the Kirby style could be mutated, and many artists went off increasingly in their own directions after that.

did he stay there long?