The character debuted as the lead feature in Marvel Super-Heroes #12 (in December 1967), written by Stan Lee and illustrated by Gene Colan. Shortly thereafter he was given his own series, commencing with Captain Marvel #1 (in May 1968). These appearances established Captain Marvel, or « Mar-Vell », as an alien of the Kree race who had come to Earth as a spy before coming to identify with his human neighbors.

The Captain Marvel series failed to register with readers, and the series was revamped by writer-artist team Roy Thomas and Gil Kane in issue #17 (in October 1969). The character was given a new uniform, designed by Gil Kane and colorist Michelle Robinson, and greater abilities. An added plot feature was the introduction of sidekick Rick Jones. Rick Jones and Captain Marvel « shared molecules » allowing only one to exist in the real world at a time. Roy Thomas stated that the intent of the change was to create a more science-fiction oriented update that was reminiscent of Fawcett Comics' original Captain Marvel, who similarly had an alter-ego that could not co-exist with the super-hero.

The change, however, was not successful, and the series was published only intermittently from 1969. It was initially canceled with issue #21 (in August 1970), though the character appeared in the Kree-Skrull War storyline in Avengers #89-96 (in June 1971 - March 1972), also written by Roy Thomas. In 1972, plotter and artist Jim Starlin decided to revamp the character.