Facing foreclosure of their homes in the "Goon Docks" area of Astoria, Oregon, to an expanding country club, a group of kids who call themselves "the Goonies" (Mikey, Data, Mouth, and Chunk) gather for a final weekend together.

Rummaging through Mikey's attic, they come across a 1632 doubloon and an old treasure map purporting to lead to the treasure of legendary pirate "One-Eyed Willy", believed to be located somewhere nearby and considered by Mikey to be the original Goonie. Seeing the treasure as their last chance to save their homes, the kids overpower and bind Mikey's older brother, Brand, and make their way to an abandoned restaurant on the coast that coincides with the map. Brand soon follows alongside Andy, a cheerleader with a crush on him; and her best friend Stef, a tomboy.

The group eventually discovers that the derelict restaurant is a hideout of the Fratelli crime family: Francis, Jake, and their mother. The Goonies find a tunnel in the basement and follow it, but Chunk leaves to alert the police after being locked in the freezer. When Chunk flags down a nearby car to go to the sheriff's station, it turns out to be the Fratellis, who imprison him with their hulking and deformed younger brother Sloth. The Fratellis interrogate Chunk until he reveals where the Goonies have gone and begin pursuit. Chunk is left behind with Sloth, whom he befriends. After Sloth frees them both, Chunk calls the sheriff, who thinks it is another one of Chunk's tall tales. Chunk and Sloth follow the trail of the Fratellis.

The Goonies evade several deadly booby traps along the tunnels, while barely staying ahead of the Fratellis. They finally reach the grotto where Willy's pirate ship, The Inferno, is anchored. The group discovers that the ship is filled with treasure, and they start filling their pockets, but Mikey warns them not to take any on a set of scales in front of Willy's skeleton, considering that to be their tribute to him.

As the Goonies are planning their escape, the Fratellis appear and strip them of their gain. The Fratellis start to bind the Goonies' hands and make them walk the plank until Chunk and Sloth arrive and distract the Fratellis long enough for the Goonies to jump overboard and swim to safety. Brand saves Andy from drowning and they kiss. The Fratellis proceed to grab all the treasure they can, including those on Willy's scales; this triggers another booby trap, which causes the grotto to cave in. With Sloth's help, the Goonies and Fratellis barely escape.

The groups emerge on Astoria's beach, where the Goonies reunite with their families and the Fratellis are arrested by the police, but Chunk prevents them from doing the same to Sloth; whom he invites to live with him, which Sloth accepts. Just as Mikey's father is about to sign the foreclosure papers, the Walshes' Hispanic housekeeper, Rosalita, discovers that Mikey's marble bag is filled with some of the ships' jewels that had not been seized by the Fratellis, ensuring enough funds to negate the foreclosure.

As the Goonies are recounting their adventure to the disbelieving police and press, everyone's attention is drawn to the Inferno, having broken free of the grotto, sailing off majestically on its own in the distance.
Cast

    Sean Astin as Michael "Mikey" Walsh, the asthmatic leader of the Goonies
    Josh Brolin as Brandon "Brand" Walsh, a high-school athlete and Mikey's older brother
    Jeff Cohen as Lawrence "Chunk" Cohen, a clumsy and gluttonous member of the Goonies and habitual fabulist
    Corey Feldman as Clark "Mouth" Devereaux, a member of the Goonies nicknamed for his cheeky tongue and Mikey's best friend
    Ke Huy Quan as Richard "Data” Wang, a member of the Goonies who is a James Bond fanatic and amateur gadgeteer
    Kerri Green as Andrea Theresa "Andy" Carmichael, a high-school cheerleader and Brand's love interest
    Martha Plimpton as Stephanie "Stef" Steinbrenner, a snarky tomboy and Andy's best friend
    John Matuszak as Lotney "Sloth" Fratelli, the deformed and much-abused, but child-hearted, son of Mama Fratelli whom Chunk befriends
    Robert Davi as Jake Fratelli, Mama Fratelli's counterfeiter son
    Joe Pantoliano as Francis Fratelli, Mama Fratelli's most lauded son
    Anne Ramsey as Mama Fratelli, the Fratellis' matriarch
    Mary Ellen Trainor as Irene Walsh, Mikey and Brand's mother
    Keith Walker as Irving Walsh, Mikey and Brand's father and a curator at the local history museum
    Lupe Ontiveros as Rosalita, the Walsh family's Mexican housekeeper who can only speak Spanish
    Curt Hanson as Elgin Perkins, Troy's millionaire father and proprietor of Astoria Country Club who is behind the foreclosures at the "Goon Docks"
    Steve Antin as Troy Perkins, the spoiled son of Elgin Perkins who is Brand's rival for Andy's attention
    Paul Tuerpe as the Sheriff
    George Robotham as a prison guard who gets fooled by Jake's feigned suicide
    Michael Paul Chan as Data's approving father

Director Richard Donner makes an uncredited cameo appearance as a sheriff's deputy.[7] The film's cinematographer Nick McLean also has a cameo as Mouth's father. The part of the dead FBI agent was performed by stuntman Ted Grossman.[8]