Eighteen thousand years ago, during the Last Glacial Maximum, there was no island. Sea levels sat more than 100 metres lower than today, and Motutapu was simply part of the North Island, surrounded by a vast coastal plain where the Hauraki Gulf now stretches. As the ice retreated and waters rose roughly 7,000 years ago, the land became an island. Maori arrived well before the eruption of Rangitoto around 1400 AD and built a broad-spectrum life here: hunting forest birds, fishing the surrounding waters, cultivating kumara in garden plots. Archaeological surveys since the 1960s have revealed that the island also served as a manufacturing site for adze, stone tools chipped from the local greywacke between 1400 and 1500 AD. Obsidian from Great Barrier Island and argillite from as far away as Nelson found their way here, evidence of trade networks stretching the length of New Zealand.

When Rangitoto erupted, it smothered Motutapu in ash and destroyed the existing settlements. But the catastrophe carried an unexpected gift: the volcanic debris produced friable, fertile soils ideal for gardening. Archaeological deposits bracketing the ash layer tell a story of adaptation. Before the eruption, residents hunted forest birds across a diverse landscape. Afterward, they shifted to intensive marine exploitation and horticulture, digging the kumara pits that archaeologists would later find scattered across the island. The Tainui ancestors of Ngai Tai ki Tamaki settled here following the eruption, and the island's name honors Taikehu, a tohunga of the Tainui canoe. For centuries, Ngai Tai maintained rights of occupation, negotiating fishing agreements with Ngati Paoa on neighboring Waiheke Island and defending their territory against incursions. In the 1820s, the threat of Hongi Hika and musket-armed Ngapuhi warriors forced the evacuation of most Hauraki Gulf islands. The Ngai Tai took refuge far to the south at Maungatautari before returning to resettle in 1836.

European settlement began in 1840 when the northern part of the island was sold to Tom Maxwell. For the next century, Motutapu operated as a pastoral farm, its 1,510 hectares divided among settlers who centered their operations around Emu Bay and Home Bay. The island developed a surprising social life. Home Bay Wharf hosted whale boat racing, greased pig chasing, and hunting parties, drawing visitors from Auckland who treated the island as an excursion destination. Three farming settlements left their mark: Home Bay still retains its homestead, seawall, and graves. Emu Bay preserves foundations of four separate building groups and isolated Norfolk pines that stand on the island's high points like sentinels from another era.

In 1936, the New Zealand military began fortifying Motutapu. Roads were formed, battery positions constructed, and by August 1938 six-inch guns were mounted in three gun pits overlooking the Hauraki Gulf. When war broke out in September 1939, the island's military population surged from 10 to 200. Plotting rooms, searchlight emplacements at Billy Goat Point, and underground command complexes followed. The US Navy, using Auckland as a staging point for the Pacific campaign, built deepwater wharfing facilities and 50 ammunition magazines between 1942 and 1943. Today these structures survive as a largely intact World War II landscape: underground plotting rooms with their command exchanges still visible, concrete pillboxes guarding against commando assault, and the gun emplacements themselves staring out across waters that never saw the enemy fleet they were built to stop. Within five years of the war's end, the entire complex was abandoned.

By the mid-19th century, between volcanic eruption, farming, and introduced pests, Motutapu had lost virtually all its native vegetation. The island that Maori had known as a forested sanctuary was reduced to grass and wet meadows. In 1992, the Department of Conservation began a restoration programme with an ambitious target: revegetate the island with native species by the 2040s. In August 2011, both Motutapu and neighboring Rangitoto were declared pest-free, clearing the way for species translocations. Takahe, saddleback, and North Island brown kiwi now move through regenerating bush that the Motutapu Restoration Trust has planted and tended. The trust's work extends beyond ecology to cultural heritage, restoring the historic Reid homestead alongside the forests and wetlands. An artificial causeway links Motutapu to Rangitoto's dark volcanic cone, connecting two islands with very different histories but a shared future. The sacred island is becoming sacred again.