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Compatriots Terenzo Bozzone finished second in the New Orleans men's race, with Graham O'Grady seventh.
Warriner clocked four hours, 16 minutes 44 seconds to head off Americans Lindsey Corbin (4hr 17min 51sec) and Amy Marsh (4hr 20min 23sec).
Warriner battled her way into the lead about 8km into the run and never looked back after that.
It was her first win since suffering a broken wrist in the Takapuna sprint triathlon in February.
"I'm so happy to get a good result, it feels I can re-start my season today. I've got some really exciting races coming up against some exciting competition, so things are looking up," Warriner said.
She will return to training camp in San Diego tomorrow before contemplating her next race for the season.
"I feel I've finally got some choices ahead of me again.
"I'm excited about getting back to ITU racing, but need to make sure my wrist is ok as you just can't afford to be giving away that sort of time on the swim at ITU.
"There are also a lot of other races out there that excite me; St Croix, Wildflower, Rev 3 to name just a few -- I'm loving being based in the States and being so central to all these iconic events."
Bozzone timed 3hr 47min 17sec to finish behind American winner Andy Potts who overtook the New Zealander on the run leg and won by just over three minutes. O'Grady timed 3hr 58min 10sec.