The New Zealand netballers have lost 46-40 to Australia in their third and final test in Auckland.
Australia had a five-goal lead, 14-9, after the first quarter, but the Silver Ferns managed to bring it back to 22-all at half-time.
They stayed in touch with the visitors, with the scores still tied, at 31 apiece, going into the last 15 minutes.
But the Silver Ferns were no match for the Diamonds' defence in that final quarter, scoring only nine goals to Australia's 15 to give the Diamond's the series win and the new Constellation Cup, which will be contested by the two sides on an annual basis.
Silver Fern mid-courter, Temapara George, says the Australian defence was harder to combat, and the changes made from the second test did not affect the result.
The Silver Ferns beat the Diamonds 59-40 in the second test in Wellington after being well beaten in the first Test in Australia, 43-48.
Australia now have the psychological edge going into next month's Commonwealth Games in India.