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."
The first race on day two saw Team NZ get away cleanly and lead around the first mark, get clear air and sail away.
Dean Barker, Glenn Ashby, Ray Davies, Jeremy Lomas and James Dagg were never troubled.
They sailed a faultless race, extending on every leg and finished 2m 27s ahead of Luna Rossa Piranha with a procession following in quick succession - Artemnis 2m 33s and Oracle Racing 5 2m 45s.
The second race was almost a carbon copy of the first with the exception of the placings at the first mark and Team NZ was second around, chaing Luna Rossa Swordfish.
On the run they rolled the Ialians rounded the leeward gate in first place and were never headed.
At the finish Barker was 45s ahead of the Luna Rossa Swordfish with Luna Rossa Piranha 1m 16s.
Leader board after four races: Team New Zealand 38, Oracle Racing 4 29, Luna Rossa Piranha 27, Team Korea 27, Energy Team 25, Luna Rossa Swordfish 24, Oracle Racing 5 16, Artemis Racing 12, China Team 4.