The Power Rangers Rocky, Adam, Billy, Aisha, Kimberly and Tommy participate with Bulk and Skull in a charity sky dive for the Angel Grove observatory in anticipation of Ryan's Comet, which will pass by in two days. Having waited too long to jump, Bulk and Skull accidentally land in a construction site, where a giant egg is unearthed from a chamber underground. The evil energy alerts Zordon, an interdimensional wizard and the Rangers' mentor, who warns them of Ivan Ooze: a morphological being bent on the conquest of Earth. Zordon sends the Rangers to return the egg to its chamber, unaware that Lord Zedd and Rita Repulsa have already freed Ivan Ooze and ordered him to destroy Zordon. Ivan leaves the Rangers to face his Ooze men while he lays siege to their Command Center and incapacitates Zordon. Meanwhile, the Rangers morph and dispatch the Ooze men before suddenly losing their powers. Making their way to the Command Center, they find it destroyed and Zordon outside of his time warp, now dying from rapid aging.
Zordon's robotic assistant Alpha 5 sends the Rangers to the planet Phaedos in hopes of obtaining the Great Power in order to save Zordon. Ivan usurps Rita and Zedd and traps them in a snowglobe, offering their minions Goldar and Mordant the choice to join him or suffer the same fate. They agree to serve him. Ivan sends a squadron of bird-like Tengu warriors to Phaedos while he hatches a plan to unearth his Ectomorphicon Titans: two massive machines he had constructed for his conquest that were buried near his chamber. He puts his ooze into mass production and, after disguising himself as a carnival wizard, he gives out free jars of it to the city's children, including the Rangers' friend, Fred Kelman. When their parents come into contact with the ooze, it hypnotizes them into becoming Ivan's work force. After Fred discovers his father missing, he finds him and the other parents at the construction site and discovers Ivan's plans.
The Rangers arrive on Phaedos and are almost killed by the Tengu until they are rescued by Dulcea, Phaedos' Master Warrior, who initially tells the Rangers to go back home. When she hears of Zordon's plight, however, she agrees to help them and takes them to a ruined temple. Once there she gives them the power of the Ninjetti, showing them their animal spirits: Rocky is the ape, Adam is the frog, Billy is the wolf, Aisha is the bear, Kimberly is the crane and Tommy is the falcon. She shows them where the monolith housing the Great Power resides, but tells them that their journey has to be without her because if she went beyond the temple, she would age as rapidly as Zordon. As the Rangers quest through the jungle, they encounter an animate dinosaur-like skeleton, which Tommy defeats before they find their way to the temple. Working together, they defeat its four guardians, unlocking the Great Power within to restore their powers.
Back on Earth, construction is completed on the machines and Ivan orders the parents to return to the construction site and leap to their dooms. Fred rushes to the rest of the kids and Bulk and Skull, partying at Ernie's, and tells them of the situation. Together they board the city's monorail and head to the construction site to save their parents. The Rangers return and call on their new Zords. They defeat one of the titans, which enrages Ivan and leads him to merge with the other machine. The Rangers form the Ninja Megazord while Tommy saves the train, whose track was damaged by Ivan. Outmatched, the Ninja Megazord is damaged; Tommy combines his Zord, creating the Ninja Falcon Megazord to fight Ivan. Billy plots a course to outer space intending to lead Ivan into Ryan's Comet. Ivan pins them down, but Aisha causes him to lose his grip and they fly out of the path of destruction. Ivan's destruction breaks his spell on the parents, who come to their senses as their kids, Bulk and Skull keep them from stepping over the cliff as Fred reunites with his father. Returning to the Command Center, the Rangers learn to their sadness that Zordon has died. Using what they learned – that all things are possible – they use the Great Power to restore the Command Center and resurrect Zordon, reuniting with him.
During the following fireworks celebration, the Rangers congratulate Fred for his bravery. When a message thanking the Rangers is lit, Bulk and Skull are offended, although they had a legitimately large part in saving lives.
In a mid-credits scene, Goldar sits on Zedd's throne and calls himself "King Goldar, the ruler of the universe" before Zedd and Rita enter, growling at their turncoat behavior. Goldar and Mordant look at each other and nervously proclaim "Uh-oh!" before the credits continue.