Julian Gardner took second place and won $1.1m in the event - which he carried from the casino in a large suitcase.
The winner was Robert Varkonyi of New York, who emerged victorious on Friday from the 33rd event which boasted a record field of 631 players.
His full house on the 161st hand of the day beat Mr Gardner.
Cheering crowds
The World Series, which runs for a month, incorporates many different competitions - but the winner is the one who beats all comers at the final event, the No-Limit Texas Hold-Em.
Mr Gardner told the Observer newspaper that he was slightly unsettled by the sheer scale of the tournament.
"Playing in the middle of cheering crowds, with loads of cameras and $3m in cash right there on the table, turns everybody into a hero and makes it tougher," he said.
Other UK players included John Shipley from Solihull, who finished seventh, and London brothers Ross and Barny Boatman.
Phil Hellmuth Jr from California, the youngest World Series of Poker winner at 24, lost a side bet with the crowd that Mr Varkonyi would not win - and as a result, had to shave his head.