The character debuted in The Brave and the Bold #28 (March 1960) in the story "Starro the Conqueror", which was also the first appearance of the Justice League of America.

The entity visits Earth and empowers three starfish; the creatures begin wreaking havoc, such as exploding an atomic bomb and absorbing its energy, kidnapping scientists and absorbing their brain power and placing the residents of Happy Harbor, Rhode Island, under mental control.

Eventually, they are stopped by the superheroes Aquaman, the Flash, Green Lantern, Martian Manhunter and Wonder Woman.

Aided by former Green Lantern Kilowog, Starro returns to his original spaceship and tricks the heroes by programming it to explode.

Controlling the minds and bodies of thousands of humans, Starro seizes power, with several members of Justice League Europe opposing the alien.

[10] During JLA and referring to itself only as It, another member of Starro's species controls the Flash and the population of Blue Valley using spores.

Although the JLA intend to intervene, they are advised against doing so by the Spectre, who reveals the alien's intention is to capture and control the heroes and use their special abilities to conquer the galaxy.

[11] This version of Starro returns and is revealed to be a scout for a larger member of the species called the "Star Conqueror".

Assisted by a homeless man resisting the entity's control, the heroes free mankind from the alien's influence.

Zoo Crew member Pig Iron battles Starro underwater, sacrificing himself as the rest of the heroes escape.

[17][18] During New 52, Starro is still linked with the Justice League via historian David Graves' book making sporadic appearances throughout.

[29] Their size can also vary from being as big as city blocks to larger than a small planetary ocean body, in which case said Starro probe can radically alter the very climate, topography, and geography within its vicinity akin to terraforming.

[30] The latest version of the Star Conqueror shows how it uses its parthenogenesic capabilities to breed microscopic clones of itself, which can be inhaled by potential victims, serving as a catalyst to affect the giant iteration's telepathic abilities.