Oracle won the start with a shrewd manoeuvre that pushed New Zealand away from the line, and then showed impressive speed on the critical upwind leg before dashing home for the victory.
New Zealand has mostly dominated the best-of-17 finals series and now holds an eight to two lead.
"We know the nation is watching us, but once you get into the start box you don't really think about that," said Grant Dalton, managing director of the New Zealand team and a grinder on their 72-foot catamaran.
The Kiwis turned in the latest of several textbook performances in moving to the brink of victory on Wednesday, and seemed to have beaten back an Oracle revival that saw the U.S. boat win two thrilling races over the weekend.
But Thursday's first race suggested the momentum could be shifting once again as Oracle showed the speed, tactics and boat handling it needs to match the polished Kiwi team.
"It's quite unbelievable that the two boats are so close in performance across a wide range of conditions," New Zealand skipper Dean Barker said after Wednesday's match-up.
New Zealand was forced to wait for a final crack at the Cup after a second race scheduled for Wednesday was canceled due to a strong sea breeze and outgoing tide that made conditions on San Francisco Bay unsafe for the high-performance but fragile AC72 catamarans.
Ellison's team won the America's Cup in Valencia, Spain in 2010 and with it the right to set the rules for this year's competition, including choosing to race on the AC72s and to hold the regatta on windy San Francisco Bay.
The Kiwis first won the America's Cup in 1995 and successfully defended it in 2000 before losing the trophy three years later to Swiss biotechnology billionaire Ernesto Bertarelli's Alinghi in a disastrous campaign that left the team in shambles.