Using a tapa cloth to animate her story, Gramma Tala (Rachel House) shares the tale of the mother island, Te Fiti, with a group of young children. Te Fiti is imbued with a powerful heart that creates life and births other islands. Unfortunately, the allure of her heart attracts other beings, and only one, the demigod Maui (Dwayne Johnson), dares to seize it. Armed with his magical fish hook, Maui travels to Te Fiti and steals her heart, a small green gemstone adorned with a spiral. This theft results in the decay of Te Fiti's island, and soon darkness begins to spread.
As Maui escapes on his vessel, he faces off against Te Ka, a monstrous entity of lava and fire that rises from the depths like a vengeful volcano. In their fierce battle, Maui suffers defeat, losing both his hook and the precious heart to the ocean depths. Gramma Tala concludes her story with a foreboding message, explaining that even a thousand years later, Te Ka and other creatures still seek the heart, with darkness growing until it consumes their island. While most of the children are left terrified, one girl, Moana (Louise Bush), is captivated by the tale. Gramma Tala assures them that one day, someone will recover the heart, unite with Maui, and restore balance.
At that moment, Chief Tui (Temuera Morrison), Moana's father, enters and reassures the children that they are safe from darkness as long as they stay within the reef. However, in his haste, he accidentally knocks over a post revealing drawings of monsters, causing chaos among the children. Amidst the panic, Moana sneaks away to the water's edge, where she discovers a baby sea turtle in distress, threatened by a flock of frigate birds. Leaving a seashell behind, she uses a large leaf to shield the turtle and safely guide it to the ocean.
After ensuring the turtle's safety, Moana witnesses a mesmerizing ripple across the water’s surface. As she picks up a glowing stone from the shore, her father calls for her, and the ocean playfully returns her to the beach on a driftwood piece, albeit without the stone. Her mother, Sina (Nicole Scherzinger), assures her that she is destined for greatness as the future chief.
As Moana grows up on her island, Motonui, she learns everything necessary to fulfill her duties. However, she feels an undeniable pull towards the ocean. Each time she approaches it, her parents remind her of her responsibilities to her people. Gramma Tala encourages Moana to listen to her inner voice and follow her heart, suggesting that it defines her true self. Chief Tui takes Moana to their island's sacred peak, revealing a towering stack of stones, hinting that one day she too will add her stone and contribute to her people's legacy.
Embracing her role as chief-in-training, Moana handles various tasks around the island, including repairing roofs and teaching children traditional dances. When a local woman presents them with failed coconut harvests, Moana proposes a new planting spot. Yet, the fishermen report unsuccessful fishing trips as well. Despite her suggestion to fish beyond the reef, her father rebuffs the idea, agitated by the risks involved.
Sina explains to Moana that Tui’s fears stem from a traumatic experience from his youth, where a boat trip ended in disaster, leaving him fearful for Moana's safety. Nonetheless, she encourages Moana to follow her passions, no matter how challenging it may be.
Struggling between her village duties and her yearning for the sea, Moana decides to venture out, taking a canoe to explore the waters beyond the reef with her pet pig, Pua. Initially, she sails with ease, but soon waves overpower the canoe, causing it to capsize and tossing Pua overboard. After a tense encounter with coral, Moana escapes and is relieved to find Pua safe. Gramma Tala arrives, light-heartedly suggesting the pig might be at fault, but quickly realizes Moana needs support.
Moana confides in Tala about her desire to place her stone on the pile, and Tala encourages her. They share a moment of connection, leading Tala to reveal a hidden cave containing their ancestors' fleet of voyaging canoes, long abandoned in the wake of Maui stealing Te Fiti's heart. Moana is overjoyed to learn that her ancestors were mighty navigators and voyagers. Tala presents Moana with the very heart of Te Fiti, signifying that the ocean has chosen her as the one destined to restore it.
With determination, Moana sets sail to find Maui, despite her initial lack of sailing expertise. After facing various trials, including a battle with mischievous coconut pirates known as the Kakamora, she earns Maui's reluctant cooperation. He begins to teach her navigation techniques, which greatly enhance her sailing skills. Together, they navigate dangerous waters toward Te Fiti, where they hope to restore the heart and bring life back to her island.
Upon confronting Te Ka, Moana faces incredible challenges, followed by a revelation about Te Ka's true identity, leading to a daring attempt to restore both the heart and balance to the islands. Ultimately, with her ancestors by her side, Moana courageously places the heart back into Te Ka, who transforms back into Te Fiti, signifying life renewed. In the end, she returns to Motonui, now ready to embrace her future as a master wayfinder with her people, guided by her grandmother's spirit and the legacy of exploration.
