It was her second world record and her fourth individual win this week, claiming all freestyle titles from 200m to 1500m.
The New Zealander pushed through the 800m in 8:27.04 but paid the price for her brave endeavours, forced to fight hard to come home in 15:55.69, two seconds clear of Canada's Brittany MacLean.
"I knew Ledecky would be pretty much ahead of the field but I didn't want to race for second place," she said."I need to be able to have some good speed at the front end of my races so it's been good to have a focus that I have been able to work on at this meet.
"I went out as hard as I could to try and stay in contact and it really hurt at the end. I felt more true to myself that I didn't just try to come second. It was a tough race. I knew it would be tough but I am happy with my effort."
It brings to an end a challenging month for Boyle, with gold and silver medals in the Commonwealth Games in Glasgow and now three medals behind the phenomena that is Katie Ledecky at the Pan Pacific Championship.
"Two big international competitions on top of each other has been quite emotionally draining but at the same time quite strengthening for the people who are really able to embrace the challenge."
It is not over quite yet for Boyle, who returns home with the New Zealand team to compete in the national short course championships in Wellington starting on 2 September.
Boyle's teammate Emma Robinson finished eighth in the 1500m freestyle in 16:44.88.
Also in action, Mitchell Donaldson finished seventh in the A Final of the 200m individual medley in 2:01.34, a fraction outside his previous best.
North Shore's Laura Quilter was seventh in the B Final of the 50m freestyle in 26.10, under her entry time but a tick slower than her heat swim.