The film was theatrically released by American International Pictures as a double feature with The Brain That Wouldn't Die.

The privates are assigned to a scouting mission that requires the inspection of a newly discovered cavern that was located near the base.

The privates are attacked by seven-foot-tall vegetable-like creatures that take them into the cavern, which is actually an alien base commanded by two statuesque women from the planet Kalar.

The alien women, Dr. Puna and Professor Tanga, reveal that they arrived on Earth with the goal of conquering the planet.

Philbrick eventually discovers that kissing Puna leaves her temporarily powerless, allowing him and Penn to escape from the cavern and its inhabitants.

After an encounter with an American Indian band, the two soldiers race back to their base to rally a defense of the Earth against the Kalar aliens.

Invasion of the Star Creatures was nominated in the category for “The Worst Vegetable Movie of All Time”, with the authors noting the monsters controlled by the Kalar aliens were played by actors wearing carrot costumes.