Sent off at odds of 13-1, Drosselmeyer defeated Fly Down by three-quarters of a length on a hot, sunny Saturday in front of 45,243 at Belmont Park.
Preakness runner-up First Dude was third after setting the pace for most of the 1 1/2-miles. Derby runner-up Ice Box finished ninth as the 9-5 favorite for trainer Nick Zito in the 12-horse field.
Drosselmeyer, a 3-year-old chestnut colt owned by WinStar Farm, won in 2:31.57. The son of Distorted Humor also gave jockey Mike Smith his first Belmont win in his 13th try.
Smith won the race by keeping his long-striding colt in the clear. They eased to the outside for the run down the backstretch, keeping First Dude within range.
Drosselmeyer made a four wide move on the final turn and continued widest of all, eventually reeling in First Dude and then holding off a late charge from Fly Down.
WinStar also owns Kentucky Derby winner Super Saver, who along with Preakness winner Lookin At Lucky did not run in the final leg of the Triple Crown.
Drosselmeyer had been an underachiever all year in finishing fourth, third and second in his last three starts. But in his first try in a Triple Crown race, and with Smith aboard for the first time, the colt turned on the speed to pull off the victory.
Game on Dude was fourth, followed by Uptowncharlybrown, Stay Put, Interactif, Stately Victor, Ice Box, Make Music for Me, Dave In Dixie and Spangled Star.
Drosselmeyer returned $28, $11.60 and $7.70. Fly Down, with John Velazquez aboard, paid $6.80 and $5.10. First Dude returned $4.90 to show.
After the race, racing officials said Uptowncharlybrown was disqualified and unplaced after a weight violation. The horse lost his lead weight pad during the race and failed to carry the required 126 pounds.
Mott, the youngest trainer inducted into racing's Hall of Fame at the age of 45 in 1998, was 0 for 13 in Triple Crown races.