The story is set in a world just like ours where some people have superhuman abilities. Two of these people, are Mr. Incredible, who is exceedingly strong, and Elastigirl, who can stretch her body into almost any shape. Mr. Incredible has a young fan named Buddy, who invents gadgets and wants to be Mr. Incredible's
sidekick, but Mr. Incredible insists on working alone. The film begins in the city of Municiberg, with a busy day of crime fighting and the wedding of Mr. Incredible and Elastigirl, who call themselves Bob and Helen Parr. Shortly afterward, lawsuits from injured bystanders generate a political backlash that forces all superheroes to stop saving the world and live normal civilian lives.
Fifteen years later, Bob and Helen live unhappily in a suburb of Metroville. Their young son Dash can run faster than the human eye can see, and their teen daughter Violet can turn invisible and create protective force fields, but the family is required to hide their powers as part of the government's Superhero Relocation Program. Their baby, Jack-Jack, appears to be an ordinary child. Bob has gained a lot of weight, and he feels frustrated by his office job with an insurance company. He regularly sneaks out to secretly fight crime with his friend Frozone, who can freeze objects and moisture in the air with his hands.
One day, Bob loses his temper and assaults his boss, who refused to let him rescue an innocent crime victim. However, before he can tell Helen he was fired, he finds a video message from a 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, is flown to the island, and disables the robot. Afterward, he happily spends time with his family and gets back into shape, still pretending to have his old job, and takes his torn superhero suit to be repaired by the famous fashion designer Edna Mode. Edna also makes a new suit for Bob.
Although Mirage told Bob she works for the government, her real employer is Mr. Incredible's old fan, Buddy, who now calls himself "Syndrome" and intends to avenge himself against Mr. Incredible and the other superheroes for shunning him. He has already killed many supers by luring them to the island to fight his Omnidroids, which he has been perfecting to eventually defeat Bob. His plan is to make people believe he is a superhero by staging a fake battle with the robot.
On his next trip to the island, Bob is attacked by the more advanced Omnidroid and barely escapes from Syndrome. Meanwhile, Helen discovers the repair on his old supersuit and visits Edna, who gives her a set of supersuits for her and the children. After learning that Bob lost his job, Helen locates him with a homing device and flies to the island in a jet, with Dash and Violet secretly stowing away and leaving Jack-Jack at home with a babysitter. Syndrome's security systems detect the homing signal and manage to capture Bob. Syndrome then shoots the jet down with some missiles, but Helen, Dash, and Violet survive and make their way onto the island. After hiding the children in the jungle, Helen sneaks into Syndrome's facility and finds Bob and Mirage, who freed him after a confrontation in which Syndrome endangered her life. Back in the jungle, Bob and Helen find the children, who triggered the Island's security system shortly after Syndrome launched a rocket to fly Omnidroid to Metroville. Syndrome captures the family and follows the robot in a jet, but they escape and follow him in a second rocket with help from Mirage.
In Metroville, Syndrome uses a remote-control device to prevent Omnidroid from harming him, but he is knocked unconscious after the robot's
artificial intelligence becomes aware of the device and shoots it off of him. When the Parrs arrive, Bob finally accepts help from his family and Frozone to defeat the robot, and they destroy the robot by using Syndrome's remote, making the robot destroy itself. Syndrome wakes up and goes to the Parrs' home and pretends to be a replacement sitter for Jack-Jack and tries to kidnap Jack-Jack, the baby uses his recently emerged superpowers to attack him. Bob and Helen save Jack-Jack after Syndrome drops him in midair, and Syndrome is killed when his cape gets caught in one of his jet's engines. Three months later, after Dash races with his school track team and Violet makes a date with a boy she likes, a new villain called the Underminer appears and the Incredibles prepare to fight him.
