'It was amazing to shoot 16 under in foursomes,' said Donald. 'We somehow gelled pretty well together in foursomes. Paul obviously got very hot with the putter both times, and that was the difference.'
Casey and Donald, who each played for Europe in this year's Ryder Cup, posted a 16 under par score in foursomes play, while going 15 under in fourballs. Casey, in the current format of this event, has finished fifth, third and second prior to winning this time around.
The Spanish duo of Sergio Garcia and Miguel Angel Jimenez, who led entering the final round, closed with a 6-under 66 to take second place at 30-under-par 258. Padraig Harrington and Paul McGinley from Ireland took third place at minus-28 after a closing 65.
The Englishmen began the day one stroke behind the Spaniards, but joined their playing partners in a tie for first with a birdie at the opening hole. Casey and Donald teamed for a birdie at the fourth from 30 feet out to take the outright lead.
The Irish duo made an early charge with birdies at one, two and five to get within one shot of the lead at minus-24. England responded with a birdie at the fifth to move two strokes ahead of Ireland and remain one shot clear of the Spanish duo, who also birdied No. 5.
The Englishmen extended their lead to two strokes with a birdie at the seventh. Spain fought back with a birdie at the eighth to get within one. Ireland joined them there with birdies at eight and nine.
Spain and England both birdied the ninth, but Casey drained a 30-footer for birdie at 10 to again give the English duo a two-shot lead. Casey made a 15- foot birdie putt to keep England rolling at Real Club de Golf Sevilla.
Casey wasn't done there. He drained a 12-foot birdie putt at the 12th, their fourth straight birdie, that padded his team's lead to four strokes. The Irish duo made their final charge with an eagle at the par-5 13th and a birdie at 14 to get within two.
Spain matched the Irish eagle at 13 to also get within two of the Englishmen's lead. Garcia and Jimenez climbed within one shot of the leaders with a birdie at the 15th.
The turning point came at the 16th. The Englishmen combined to birdie the par- 5, while the Spaniards faltered to a bogey after Garcia dropped his second shot into the water, before missing a 5-foot par putt to fall three strokes back with two holes to go.
The English team needed the cushion as they bogeyed the last and Spain birdied the closing hole to set the final margin of one shot.
'Because we're such good friends and we trust each other's game, we played as good of golf as when we played in the Walker Cup,' Casey said. 'You know, it's one of those partnerships that I think we'll always play good golf together. I can't explain it. It's just one of those things that clicks.'
Spain is a four-time winner of this event, but the second place showing by Garcia and Jimenez was the nation's best since a runner-up finish in 1999. Spain last won in 1984.
'Of course we are disappointed, but you have to give a lot of credit to the English team,' said Garcia, who like Jimenez was the Englishmen's Ryder Cup teammate this year. 'I think Paul and Luke played unbelievably today, to go out there on Sunday in the World Cup and shoot 8 under in foursomes is a great effort. We tried as hard as we could, but we didn't get lucky.'
Rory Sabbatini and Trevor Immelman, the 2003 champions from South Africa, posted a final-round 68 to take fourth place at 25-under-par 263.
The Austrian team of Martin Wiegele and Markus Brier, who gained entry into the event when the team from Thailand withdrew, closed with a 67. They shared fifth place at 23-under-par 265 with Holland's duo of Robert-Jan Derksen and Maarten Lafeber.
Kariem Baraka and Marcel Siem, the team from Germany, tied for seventh at minus-21 thanks to a final-round 68. They were joined there by Sweden (Joakim Haeggman & Fredrik Jacobson) and the United States (Scott Verplank & Bob Tway), as those teams both posted even-par 72s in the final round.