After their disastrous capitulation in the cup regatta in San Francisco four years ago, the Kiwis would have been intent on gaining an upper hand early and seemed to be cruising home mid-race.
Emirates Team NZ made a key change to their crew for their second race of the day, bringing Olympic cyclist Simon van Velthooven on board for former rower Joe Sullivan to add grunt to cycle-grinding station.
For the first time in America's Cup history, the holders have been allowed to contest the challenger series as part of their preparation, allowing them to assess themselves against their opponents.
Oracle skipper Jimmy Spithill held the slight early advantage, establishing a five-second advantage at the second mark.
As both teams jockeyed for position down the third leg, TNZ tacked the better and moved past their archrivals to build a 20-second buffer by the next mark.
But down the fifth leg, the Americans came back strongly and almost drew contact with the NZ boat, as they rounded the fifth mark. That proved the crucial moment, with Oracle easing away for a six-second win.
Both Emirates Team NZ and Oracle warmed up for their showdown with easy wins over France, one of the lesser fancied teams in the qualifier series.
The Kiwis were two minutes 33 seconds better than the French, while USA were two minutes 11 seconds clear.
