Briton became the first player to win the orders of merit on both sides of the Atlantic on Sunday while Spain's Alvaro Quiros lifted the European Tour's season-ending Dubai World Championship title.
World No. 1 Donald shot a closing 66 to finish third in the tournament on 16-under 272, one behind fellow countryman Paul Lawrie (67) and three adrift of Quiros (67).
Donald, who had already clinched the US PGA Tour money list in October, picked up $1.5 million (957.5 thousand pounds) for landing the European order of merit and another $487,500 for his performance at the Greg Norman-designed Earth course.
"I'm extremely proud," the 34-year-old Donald said. "This is something I've been thinking about for the last half of the season.
"I didn't think it was possible to win the money lists on both tours. This was never going to be an easy week but it has capped off an amazing year for me," he said referring to his four victories and a host of top-10 finishes.
The 28-year-old Quiros collected the first prize of $1.25 million after making it a Dubai double -- he also lifted the Desert Classic crown in February -- by coaxing home a curling 50-feet eagle putt at the 18th.
"Obviously I was lucky to hole that long putt," said the smiling Spaniard on another scorchingly hot day at the Jumeirah Golf Estates. "I love playing in Dubai, the great weather helps a lot.
"Long hitters like me also have an advantage here."