A group of elite mercenaries known as the Expendables embark on a daring mission in the Gulf of Aden off the coast of Somalia to thwart local pirates from carrying out their threat to execute hostages. This formidable team is led by Barney Ross, who is joined by former SAS operative and knife expert Lee Christmas, martial artist Yin Yang, sniper Gunnar Jensen, and their skilled companions. During a high-stakes encounter, Jensen sparks a fierce firefight, resulting in numerous pirate casualties. A clash of ideals arises between Yang and Jensen over the ethics of executing a captured pirate, prompting Ross to step in and ultimately dismiss Jensen from the team due to his troubled mental state.
The narrative intensifies as Ross and his rival mercenary, Trench, meet the resourceful Mr. Church who presents them with an opportunity to take down the ruthless dictator General Garza on the fictitious island of Vilena. Distracted with personal matters, Trench suggests that Church give the contract to Ross. Meanwhile, Christmas confronts emotional turmoil when he discovers that his girlfriend, Lacy, has left him for another man. Upon their arrival in Vilena, Ross and Christmas connect with a local contact named Sandra. The situation escalates when they intercept Garza’s troops, rescuing Sandra from capture. However, they soon uncover that Garza is being manipulated by ex-CIA operative James Munroe, alongside his henchmen.
After deciding to back out of the mission, Ross experiences a change of heart and leads a counter-attack against Garza's forces, showcasing their lethal skills. Jensen, feeling betrayed, aligns himself with Garza and Munroe, deepening the conflict. Christmas, unable to ignore Lacy’s plight, defends her from her new abusive partner, demonstrating his capabilities in a particularly brutal confrontation.
As the plot unfolds, Ross learns of Munroe’s darker ambitions and how he exerts control over Garza through fear. Haunted by his past during the Bosnian War, the team's emotional coordinator, Tool, confides in Ross, revealing how his guilt has plagued him. When Sandra is captured and tortured for information, Ross makes the decision to rescue her with Yang at his side.
The ensuing operation to save Sandra leads to a chaotic chase filled with tension and violence. In a climactic showdown, the Expendables infiltrate Garza’s heavily fortified compound, engaging in a fierce battle that showcases their expertise and teamwork. Ross courageously saves Sandra from imminent danger, battling against Munroe's formidable forces.
As chaos unfolds, Garza eventually sees Munroe for what he truly is, leading to a series of explosive confrontations. The team fights valiantly, utilizing an arsenal of high-powered weaponry to take down Garza’s army and confront Munroe in a final showdown. In a twist of camaraderie and honor, Ross chooses to forgo payment for their mission, instead choosing to give the funds to Sandra to aid in the rebuilding of her village.
The triumphant Expendables celebrate their victory in a tattoo parlor, showcasing their strong bond and resilience, while Christmas and Tool engage in a light-hearted challenge of skill, wrapping up their harrowing journey with a moment of levity and camaraderie.
