The film unfolds on a picturesque island where Moana (Auli’i Cravalho), along with her adorable pets Pua the pig and Heihei (Alan Tudyk), embarks on an adventurous quest through the lush forest in search of lost artifacts belonging to her ancestors. Her dream is to uncover connections with other oceanic tribes, but her initial finds are limited to an ancient pot adorned with ancestral carvings. Returning home to Motunui, Moana is welcomed warmly by her parents, Chief Tui (Temeura Morrison) and Sina, as well as her adoring little sister Simea. The community praises Moana’s prowess as a legendary wayfinder, a title she earned through her endeavors alongside Maui (Dwayne Johnson) to protect their homeland.
Meanwhile, deep in the ocean's depths, Maui stumbles upon a cave inhabited by a witch named Matangi ([Awhimai Fraser]). Matangi, serving the vengeful god Nalo (Tofiga Fepula’i), informs Maui that to locate the submerged island of Motufetu—lost beneath the waves due to Nalo's wrath—he will need Moana's assistance. Despite his hesitations concerning her safety, Maui is captured by Matangi, rendering him helpless.
As night falls, Moana joins her tribe for a ceremonial event where a sudden lightning flash reveals a vision of her ancestor Tautai Vasa ([Gerald Ramsey]). He recounts how his crew was once on a quest to find Motufetu but was thwarted by a tempest conjured by Nalo. In a haunting display, Tautai reveals a bleak future where Moana's home becomes desolate unless she acts to unite the scattered oceanic tribes. Awakened by her vision, she understands that the lost island is her ultimate destination. Despite her parents’ anxieties and her sister Simea's tears, Moana is resolute in her decision to embark on this perilous journey, inspired by the spirit of her grandmother Tala (Rachel House).
Determined, Moana gathers her loyal companions: Pua, Heihei, and three enthusiastic new crew members—Moni ([Hualalai Chung]), a tapestry artisan with a deep admiration for Maui; Loto ([Rose Matafeo]), a young and resourceful canoe builder; and Kele ([David Fane]), an irritable farmer contributing vital supplies for their quest. Although Simea attempts to stow away, Moana reassures her sister that she will return, showcasing the ocean's dynamic responsiveness to them.
Set sail on a voyage filled with promise, following a shooting star that acts as their guide (“What Could Be Better Than This?”). However, their journey takes a turn when this celestial body breaks apart to reveal the Kakamora, rowdy little warriors intent on their mischief. As Moana strives to navigate her crew away from these coconut marauders, they are tranquilized and taken aboard the Kakamora's ship, leading to another encounter with a gigantic clam-like creature.
Fortuitously, the Kakamora reveal their plight through Moni’s translations, indicating they were left adrift after Motufetu vanished. This shared history kindles an alliance, and they agree to assist Moana's crew in defeating the fearsome clam. Yet, their endeavors lead them deeper into peril when they tumble into a cave. In a twist of fate, Maui breaks free from his confines and deduces Moana is in jeopardy. As he reunites with the crew, Moana herself meets Matangi and learns that the witch is bound within the cave by Nalo's will. Matangi extends her support to Moana, helping her to find an escape route (“Get Lost”) while expressing confidence in Moana’s ability to triumph over Nalo.
As they approach the fabled Motufetu, Nalo’s curse weighs heavily upon them, hindering the ocean’s assistance. A confrontation with sea serpents results in chaos, narrowly sparing Moni’s life thanks to Maui's intervention while the crew’s canoe wrecks on a foreign shore. While Moana faces dismay, Maui rallies her spirits (“Can I Get a Chee Hoo?”), encouraging a resurgence of hope which ignites her determination to restore the canoe and regain their course.
The group bravely navigates into Nalo's tempest, the very barrier preventing mortals from finding Motufetu. Maui, attempting to draw Nalo’s ire away from the crew, faces severe consequences when a bolt of lightning strips him of his divine essence while Moana plunges into the depths, calculating that her touch may unravel the curse. Yet, a terrifying fate befalls her when lightning strikes, seemingly extinguishing her life. Overcome with sorrow, Maui mourns and raises a song to honor her (“Mana Vavau”), which calls forth the spirits of Moana's ancestors, including Tautai and Gramma Tala, to breathe new life into her. As she awakens, a wayfinder tattoo etches itself upon her arm; with renewed vigor, Maui reclaims his power and retrieves Motufetu from the depths of the ocean (“Beyond Reprise”).
Following a triumphant resurrection, Moana sounding a conch shell signals the unification of the lost tribes, and the Kakamora joyfully rediscover their own home. Returning to Motunui, Moana shares her experiences while introducing Simea to Maui, who chuckles as she mimics her sister’s past antics. With their homeland reconnected to the larger world (“We Know The Way”), Moana and her adventurous crew depart to explore new horizons.
In a post-credits scene, the vengeful god Nalo appears in human form to confront Matangi for her betrayal in aiding Moana, vowing retaliation against humanity. The scene intensifies when Tamatoa (Jemaine Clement) joins in the plot for revenge, only for Nalo to strike him down with a surge of lightning, hinting at the ongoing adventures that await.
