World War II veterans Danny Ocean (Frank Sinatra) and Jimmy Foster (Peter Lawford) recruit nine of their comrades from their unit in the 82nd Airborne to simultaneously rob five Las Vegas casinos: the Sahara, Riviera, Desert Inn, Sands, and Flamingo.
The gang (the “eleven” of the title) plans the elaborate New Year’s Eve heist with the precision of a military operation. Josh Howard (Sammy Davis Jr.) takes a job as a sanitation worker driving a garbage truck while others get jobs at the various casinos. Sam Harmon (Dean Martin) entertains in one of the hotel’s lounges. Demolition charges are planted on an electrical transmission tower and the backup electrical systems are covertly rewired in each casino. At midnight, New Year’s Eve, the tower is blown up and the Las Vegas Strip goes dark as the inside men sneak into the cages and hold up the cashiers and then dump the bags of loot into the hotels’ garbage bins. A garbage truck driven by Josh picks up the bags and passes through the police blockade. Everything appears to have gone off without a hitch.
However, the gang’s electrician, Tony Bergdorf (Richard Conte), drops dead of a heart attack in the middle of the Strip. This raises the suspicions of police, who wonder if there is any connection. Reformed mobster Duke Santos (Cesar Romero) offers to recover the casino bosses’ money for a percentage. Since the robbery was well organized, he assumes it was a mob operation but his mob connections tell him they were not involved. But Duke is engaged to Foster’s mother (Ilka Chase), who casually mentions that Foster and Ocean, who fought together in the army, are both unexpectedly in Las Vegas. He has also learned about Bergdorf’s military record from the police. By the time Bergdorf’s body arrives at the mortuary, Santos has pieced together the puzzle.
Santos now confronts the thieves, demanding half of their take. In desperation, they hide the money in Bergdorf’s coffin, setting aside $10,000 for his widow (Jean Willes). The group plans to take back the rest of the money, making no payoff to Santos, after the coffin is shipped to San Francisco. This plan backfires when the funeral director talks Bergdorf’s widow into having the funeral in Las Vegas—where the body is cremated, along with all of the remaining money.