Costa Schmid was second nearly two seconds behind with Belmonte Garcia out-finishing Friis for third.
In the two days of competition at Eindhoven, Boyle has obliterated the national records in the 200m, 400m and 800m freestyle with today's victory, like the 800m freestyle yesterday, rattling the world record mark of 3:54.85 set by Camille Muffat of France last year.
Earlier North Shore's Shaun Burnett finished 14th fastest in the heats of the 100m butterfly in 54.87.
The pair now head to Germany for the second leg of the FINA Arena World Cup in Berlin on Saturday and Sunday(local time).
Day 2 Results:
Final:
400m freestyle: Lauren Boyle (NZL) 3:55.16, 1 (NZ Record); Melanie Costa Schmid (ESP) 3:56.84, 2; Mireia Belmonte Garcia (ESP) 3:58.21, 3.
Heats:
400m freestyle overall: Costa Schmid 4:01.85, 1; Boyle 4:02.17, 2; Sharon van Rousendaal (NED) 4:02.94, 3.
100m butterfly overall: Steffen Deibler (GER) 49.70, 1; Thomas Shields (USA) 50.35, 2; Nikolay Skvortsov (RUS) 51.08, 3. Also: Shaun Burnett (NZL) 54.87, 14.