In the Hulk's debut appearance in The Incredible Hulk #1, by writer Stan Lee, penciler Jack Kirby and inker Paul Reinman, the Hulk was gray rather than his later longtime trademark green. Writer and Marvel editor-in-chief Lee had wanted a color that did not suggest any particular ethnic group. Colorist Stan Goldberg, however, insisted to Lee that the coloring technology at the time could not present the color gray clearly or consistently, resulting in different shades of gray, and even green, in the issue. So in issue #2 and after, Goldberg colored the Hulk's skin green.[2] Reprints and retellings of the Hulk's origin during the next two decades feature him with green skin from the beginning, but starting with vol. 2, #302 (Dec. 1984), the Hulk was again shown as having been gray in flashbacks to early appearances. This was confirmed in vol. 2, #318 (April 1986), which states that the Hulk was gray at the time of his creation. All subsequent reprints of the first issue have reinstated the original gray coloring.

In early stories, Banner becomes the Hulk at sunset each day, but he later transforms whenever he becomes angry or panicked. Another method was shown in Fantastic Four #12 (March 1963), featuring the Hulk's first battle with The Thing; Banner intentionally uses a gamma ray machine of his own design to transform into the Hulk. Many early Hulk stories involve General Thaddeus "Thunderbolt" Ross trying to capture or destroy the Hulk with his U.S. Army battalion, the Hulkbusters, at his side. Ross' daughter, Betty, loves Banner and criticizes her father for pursuing the Hulk. General Ross' right-hand man, Major Glenn Talbot, also loves Betty and is torn between pursuing the Hulk and trying to gain Betty's love more honorably. Rick Jones serves as the Hulk's friend and sidekick for a time. Later, another teenager, Jim Wilson, also befriends the Hulk.

The original series was canceled after six issues, with the finale cover-dated (March 1963). Lee had written each story, with Kirby penciling the first five issues and Steve Ditko penciling and inking the sixth. The character immediately guest-starred in Fantastic Four #12 (March 1963), and became a founding member of the Avengers for a brief two issues of that superhero team's eponymous series (Sept. & Nov. 1963), and returning as an antagonist in issues #3 & #5 (Jan. & May 1964). He then guest-starred in The Amazing Spider-Man #14 (July 1964).

Around this time, co-creator Jack Kirby received a letter from a college dormitory stating the Hulk had been chosen as its official mascot. Kirby and Lee realized their character had found an audience in college-age readers.