Herald Island is located in the Upper Waitematā Harbour between Whenuapai (to the west) and Greenhithe (to the east).

It is relatively flat and low-lying, though it rises slightly at the eastern end The island is connected to the mainland at its western end by the Kingsway Road causeway, which crosses 400 metres (440 yd) of marshy tidal zone.

A large mudflat lies along the southwestern edge of the island, extending towards the suburb of Hobsonville to the south.

Two main roads, The Terrace and Ferry Parade, run parallel to the northern and southern shores of the island respectively.

[5] During the Ngāti Whātua/Te Taoū war with Waiohua, the twin Waiohua chiefs Hūpipi and Hūmātaitai from Ōrākei were killed at Herald Island by a Ngāti Whātua war party.

[4] In 1953, the island joined the Waitakere Riding of the Waitemata County, having previously not had any form of local government.

[8] The island was linked to the mainland by a causeway in 1957,[4] for which Waitemata County Council charged residents a special rate of 5·878d.