Superpeople, or "Supers", are people with superhuman abilities. Mr. Incredible is exceedingly strong, and Elastigirl can stretch her body into almost any shape. Mr. Incredible has a foolhardy young fan named Buddy, who invents gadgets and gets into danger while trying to help him. Mr. Incredible tries to avoid Buddy and prevent him from getting hurt. When Elastigirl helps Mr. Incredible, they bicker over who deserves credit for saving the day.
The film begins as Mr. Incredible and Elastigirl marry each other, calling themselves Bob and Helen Parr. Shortly afterward, lawsuits from injured bystanders lead to a political backlash that forces all superheroes to stop saving the world and live normal lives.
Fifteen years later, Bob and Helen live unhappily in a suburb of Municiberg. Their young son Dash is able to run faster than the human eye can see, and their teen daughter Violet can turn invisible and create spherical force fields, but they are not allowed to reveal their powers. The baby, Jack-Jack, appears to be an ordinary child. Bob has gained a lot of weight, and he feels frustrated by his office job in an insurance company. He regularly sneaks out to secretly fight crime with his friend Frozone, who can freeze things by spraying them with ice.
One day, Bob is fired from his job for losing his temper and assaulting his boss, who refused to let him rescue an innocent crime victim. However, before he can reveal this to Helen, he finds a video message from a beautiful woman named Mirage, who offers him a large sum of money to stop Omnidroid 9000, an out-of-control robot on a remote island. Bob accepts the offer, and he disables the robot after being flown to the island. Afterward, he takes his torn superhero suit to be repaired by Edna Mode, the famous fashion designer who originally made it. Edna also makes new suits for Bob and his family.
With plenty of money and satisfying work, Bob happily spends his days getting back into shape, still pretending to have his old job. However, his next trip to the island is a trap: Omnidroid and the island are owned by Mr. Incredible's old fan, Buddy, who now calls himself Syndrome and intends to avenge himself against Mr. Incredible and the other Supers for shunning him To Do It Hired Bowser Koopa's Thugs Including: Professor Ratigan, Fidget, Team Rocket (Jessie, James, Meowth), And The Shadow Man Known As Dr. Facilier They has already killed many Supers by luring them to the island to fight Omnidroid, improving its design as they revealed its weaknesses. His plan is to make people believe he is a Super by staging a fake battle with the robot. Bob is attacked by Omnidroid and barely escapes from Syndrome.
Meanwhile, Helen discovers the rip in Bob's old supersuit. She visits Edna, who gives her the new set of suits and helps her locate Bob with a homing beacon, but Syndrome's security system detects the homing signal and captures him. Helen flies to the island in a jet, with Dash and Violet secretly stowing away and Jack-Jack at home with a babysitter, and Helen, Dash, and Violet make their way onto the island after being shot down by missiles. After hiding the children in the jungle, Helen sneaks into Syndrome's facility to rescue Bob, only to find him embracing Mirage, who freed him after a confrontation in which Syndrome refused to save her life. After some bickering, Bob and Helen regroup with the children, who triggered the Island's security system shortly after Syndrome launched a rocket to fly Omnidroid to Municiberg. Syndrome eventually captures the family and follows the robot in a jet, but they follow him in a second rocket after Mirage helps them escape.
In Municiberg, Syndrome uses a remote-control device to prevent Omnidroid from harming him, but the robot's artificial intelligence becomes aware of the device and shoots it off of him. When the Parrs arrive, they and Frozone defeat the robot, and when Syndrome tries to kidnap Jack-Jack, Jack-Jack uses his new superpowers to attack him. Syndrome drops Jack-Jack in midair, and Jack-Jack is saved by Bob and Helen.
Demonstrating the wisdom of Edna's refusal to add capes to her supersuits, Syndrome is killed when his cape gets caught in the engine of his jet. Sometime later, after Dash's first race with his school track team, a new villain appears and the Incredibles prepare to fight him.