A group of elite mercenaries, the Expendables, are deployed to the Gulf of Aden off the coast of Somalia to halt local pirates from executing the hostages. The team consists of leader Barney Ross (Sylvester Stallone), former SAS soldier and blades specialist Lee Christmas (Jason Statham), martial artist Yin Yang (Jet Li), sniper Gunnar Jensen (Dolph Lundgren), weapons specialist Hale Caesar (Terry Crews) and demolitions expert Toll Road (Randy Couture). Jensen instigates a firefight, causing casualties for the pirates. Yang and Jensen fight over moral disagreements about hanging a pirate, with Ross finally intervening. As a result of his psychological problems, Ross reluctantly releases Jensen from the Expendables.
Ross and his rival mercenary leader Trench (Arnold Schwarzenegger), go to see Mr. Church (Bruce Willis) who names himself after the church they meet in. He offers them a mission in Vilena, a fictional island in the Gulf of Mexico, to overthrow a brutal dictator, General Garza (David Zayas). Busy with other things, Trench gives the contract to Ross. Christmas visits his girlfriend, Lacy (Charisma Carpenter), whom he discovers has left him for another man, Paul. Ross and Christmas do initial reconnaissance after meeting with their contact, Sandra (Gisele Itié), only for the mission to go awry. Ross learns that Garza is backed by ex-CIA agent James Munroe (Eric Roberts) and his henchmen Paine (Steve Austin) and The Brit (Gary Daniels), who manipulate and keep Garza in power by making his people fear him. Sandra is revealed to be Garza's daughter. Ross decides to abort and causes casualties among the army as they escape. Meanwhile, Jensen approaches Garza and Munroe to help their side.
Christmas visits Lacy again to find that Paul has beaten her. Christmas defeats Paul and his friends, showing Lacy what he does for a living and winning her over. Ross, Christmas, and Yang deduce that Mr. Church is a member of the CIA and that the real target is Munroe, as the CIA could not kill one of their own. Mission coordinator and former teammate, Tool (Mickey Rourke) makes an emotional confession to Ross about letting a woman commit suicide during the Bosnian War. Hearing this, Ross decides to go back for Sandra. Yang tags along, and they are chased on the road by Jensen in an intense shootout. The pursuit ends in an abandoned warehouse, where Yang and Jensen fight a second time. Jensen attempts to impale Yang on a pipe, only for Ross to shoot Jensen. A wounded Jensen makes amends and gives the layout of Garza's palace. Ross boards the plane with Yang and finds the rest of team, ready to aid their friend.
The Expendables infiltrate Garza's compound. Christmas, Yang, Caesar, and Toll plant explosive charges throughout the site. When Garza has a change of heart after Munroe tortures his daughter, Munroe kills him. The entire team fights and shoots their way through Garza's soldiers. Ross and Caesar manage to destroy the helicopter Munroe was to escape on. Christmas and Yang manage to kill The Brit while Toll kills Paine. Ross and Christmas catch up to Munroe and kill him, saving Sandra. Instead of taking the payment for the mission, Ross gives it to Sandra to restore Vilena. The team celebrates their victory at Tool's tattoo parlor, with the reformed and recovering Jensen. Christmas and Tool challenge each other to a game of knife throwing and Christmas recites a poem about his respect for Tool, before throwing the knife perfectly in the center of the board.
