Players assume the role of Roger Wilco, a lowly space janitor, who becomes involved in rescuing a pair of computer programmers from a sinister video game company.

Forced to find a way out, he discovers a derelict spaceship, the Aluminum Mallard, in the freighter's garbage hold.

Visiting the desert planet of Phleebhut, he find himself confronted by an Arnold Schwarzenegger-like android terminator, who was sent to deal with him for failing to pay for a whistle in the previous game.

At an orbital Monolith Burger station, Roger comes across a hidden message in an arcade game he plays, stating that its programmers (known as Two Guys) were abducted by ScumSoft, a sinister video game company on the Planet Pestulon - owned by Elmo Pug, leader of the "Pirates of Pestulon".

Deciding to rescue them, he visits a lava moon orbiting the planet Pestulon to neutralize a shield generator.

Heading to the planet's surface, Roger uses his invisibility belt to infiltrate the base, and secures a disguise in the form of janitor overalls.

Roger delivers the two game designers to Sierra On-Line's president, Ken Williams, before departing the planet to return home after being turned down for a janitorial job.

The mechanics of the game are similar to those of Lunar Lander, with the exception that the chicken rebounds unharmed if it strikes the trampoline too forcefully.

The game features a scene at ScumSoft where parody versions of Sierra's president, Ken Williams, and director of operations, Rick Cavin, are depicted as overseers cracking whips over software developers in cubicles.

[7] In the September 1989 edition of C&VG (Issue 94), the reviewer gave the Atari ST version of Space Quest III a score of 83%, calling it "enjoyable and addictive".

He did criticize the long loading times for each screen, and the computer's habit of prompting a disk change before the save sequence was finished.

"[17] According to Sierra On-Line, combined sales of the Space Quest series surpassed 1.2 million units by the end of March 1996.