Barney Ross leads the "Expendables", a band of highly skilled mercenaries including knife enthusiast Lee Christmas, martial arts expert Yin Yang, heavy weapons specialist Hale Caesar, demolitionist Toll Road and loose-cannon sniper Gunner Jensen. When the group is commissioned by the mysterious Mr. Church to assassinate the merciless dictator of a small South American island, Barney and Lee head to the remote locale to scout out their opposition. Once there, they meet with local rebel Sandra and discover the true nature of the conflict engulfing the city. When they escape the island and Sandra stays behind, Ross must choose to either walk away and save his own life - or attempt a suicidal rescue mission that might just save his soul.

Barney Ross is approached by CIA man Church, who wants him and his guns for hire to go to the former Soviet Union to retrieve something that was on a plane that crashed. Church doesn't tell him what he is getting. And Church sends a woman, Maggie with him to make sure he gets it. They find the plane and get the thing but some men take one of Barney's people hostage and the leader tells him to give him what they got or he'll kill his hostage. They give it to him but he kills his hostage anyway. Barney asks Maggie what was so important about that thing. She says that it showed the location of a Russian plutonium storage mine. Barney decides to track the man down and deal with him. They track them down and discover that the man they seek is Vilain who leads a group known as The Sangs and that they have taken all the men from the surrounding villages to work the mine.

Barney (Stallone), Christmas (Statham) and the rest of the team comes face-to-face with Conrad Stonebanks (Gibson), who years ago co-founded The Expendables with Barney. Stonebanks subsequently became a ruthless arms trader and someone who Barney was forced to kill... or so he thought. Stonebanks, who eluded death once before, now is making it his mission to end The Expendables -- but Barney has other plans. Barney decides that he has to fight old blood with new blood, and brings in a new era of Expendables team members, recruiting individuals who are younger, faster and more tech-savvy. The latest mission becomes a clash of classic old-school style versus high-tech expertise in the Expendables' most personal battle yet.