Team New Zealand is leading on points after four fleet races at the America's Cup World Series Naples regatta.
Starting day two on equal first with Oracle Racing 4, Barker began where he left off from day one - with a win.
The team's scoreline for Naples reads 8, 10, 10, 10, which translates to 38 points on the leader board, nine ahead of Oracle Racing 4, skippered by James Spithill.
Team NZ skipper Dean Barker said the team's crew-work was excellent.
"With conditions sharply different from yesterday - eight to 12 knots and flat water - life on board was much easier and we made the most of it. The boys we slick in all the manoeuvres and boat speed felt good."