Fewer tuned in for races three and four on Monday morning, which had an average audience of 280,500.
The audience for this year's sailing event has already beaten the highest rated race in the 2007 America's Cup in Valencia which 270,300 people watched. However, those races were held between 1am and 2am NZ time.
TVNZ's head of television, Jeff Latch, said the network was "rapt with the performance of the America's Cup live match races".
The Sunday morning races won 63 per cent of the audience at the time - more than three times higher than the closest comparable race in 2007.
"We expect numbers to build, particularly if Oracle win one or two more races as it gets closer to the end," Mr Latch said.
Herald head of news and online editor Cathy O'Sullivan said there had been huge interest in the Cup among nzherald.co.nz readers in the past week. Stories, video and comment pieces on the event had been among the most read and watched pieces of content across all of the Herald's online platforms for the past week, she said. "The live updates on race three and four on Monday saw huge engagement."
Follow all the action from races five and six from 8am.