The three male Gray's beaked whales, one adult and two sub-adults, were found beach cast at Whangaparapara on Monday evening. One animal was already deceased.
The two live whales were successfully refloated, but both were eventually found dead onshore.
DOC Operations Manager George Taylor said his staff put in a big effort to rescue the animals.
"We got them refloated and then stayed with them as long as we could, but ultimately that wasn't enough to save them – naturally we are all disappointed and saddened at the loss of these magnificent creatures."
Mr Taylor said there was no obvious reason the whales had come ashore.
Scratch marks from rubbing against rocks during stranding and cookie-cutter shark wounds and scars were typical of the injuries seen on Gray's beaked whales, which are among the most commonly stranded species along New Zealand's east coast.
DOC staff worked with Ngāti Rehua Ngātiwai ki Aotea to ensure the dead whales were given an appropriate farewell and burial following collection of routine samples and measurements.
