A tribe of cats called the Jellicles must decide yearly which one will ascend to the Heaviside Layer and come back to a new Jellicle life.
Victoria, a young white cat, is dropped in the streets of London by her owner in the middle of the night. The alley cats witnessing this introduce themselves to her as the “Jellicles”. Two toms, meek magician Mr. Mistoffelees who develops a crush on Victoria and the loyal Munkustrap, and two queens, the snooty Cassandra and Demeter, take Victoria under their wing and show her the world of the Jellicles as they hype up the Jellicle Ball, an annual ceremony where cats compete for the chance to go to the Heaviside Layer and be granted a new life.
Throughout the film, the competitors are introduced and express their contributions to the community: Jennyanydots, a domestic tabby, boosts the productivity of mice and roaches; the Rum Tum Tugger, a flirtatious tom who riles up the others; Bustopher Jones, a bourgeois cat who boasts about his weight and shares food scraps from the garbage; Skimbleshanks, a tidy ginger cat who taps along the railway; Gus, an aged theatre cat who has played some of the biggest roles in history; and Macavity, a villainous stray with the power to apparate and who kidnaps the other contestants (save for Tugger) in order to be made the Jellicle Choice by default.
Victoria also happens to meet the mischievous twins Mungojerrie and Rumpleteazer who enjoy causing trouble and messing with things in the house of their human family. They convince Victoria to join in the fun, but leave her tangled up in some necklaces when the family dog is alerted to their presence. Luckily, Mr. Mistoffelees comes to rescue Victoria, distracting the dog and escaping with her. They return to the group, just in time to see the arrival of the tribe’s wise and beloved matriarch Old Deuteronomy. The Jellicle Ball commences inside the abandoned Egyptian Theatre. Victoria dances a ballet solo in the moonlight but is distracted by Cassandra harassing Grizabella, a former member of the tribe who was banished for, among other things, her past allegiance with Macavity. Victoria relates to Grizabella’s feelings of abandonment. As Grizabella slinks away into the streets, Old Deuteronomy witnesses their quiet camaraderie and assures Victoria that she can become a Jellicle herself in time.
The Ball is interrupted by femme fatale Bombalurina, who performs a song and dance number dedicated to Macavity: a distraction to incapacitate the party with catnip. Macavity arrives, demanding to be made the Jellicle Choice. Old Deuteronomy deems him unworthy and is subsequently kidnapped and placed with Macavity’s other victims. As the Jellicles recuperate, distraught over their leader’s disappearance, Victoria suggests that Mr. Mistoffelees use his powers to conjure Old Deuteronomy back. He tries a few times, eventually making Old Deuteronomy reappear. The cats rejoice and praise Mr. Mistoffeles; he and Victoria dance together and become mates. Meanwhile, Jennyanydots, via a costume change, frees herself and the other cats kidnapped by Macavity. Macavity apparates away, leaving his lackey to walk the plank at the mercy of the emancipated cats.
Grizabella returns to the Egyptian. Victoria vouches for her and urges her to sing her true feelings. Grizabella proceeds to sing a passionate ballad about her mistakes, her former glory, and her beauty, sentiments that touch the hearts of the Jellicles. Old Deuteronomy names Grizabella the Jellicle Choice and sends her off to the Heaviside Layer in a chandelier (repaired by Mr. Mistoffelees’ magic to float like a hot air balloon). Macavity, in one last attempt to reach the Heaviside Layer, leaps onto a rope from the chandelier but falls onto Nelson’s Column. The Jellicles, reunited with their kidnapped brethren, and perched on a lion statue, watch Grizabella ascend as the morning sun appears above the horizon. After the congregation disperses, Old Deuteronomy welcomes Victoria to the tribe.
In London at night, a car drives up and tosses a cat in a bag out into the streets as other street cats watch in curiosity. From it emerges a white cat named Victoria (Francesca Hayward). She is discovered by a tribe of cats known as Jellicle cats, including Munkostrap (Robbie Fairchild), Mr. Mistoffelees (Laurie Davidson), Skimbleshanks (Steven McRae), and others surround her and sing “Jellicle Songs for Jellicle Cats”, explaining that they are the Jellicle cats.
When the cats ask for her name, she tells them Victoria, which they laugh at, asking for her real name. Munkostrap leads the cats in explaining that Cats truly have multiple different names in “The Naming of the Cats”. They invite Victoria to the Jellicle ball that evening, and not understanding, Munkostrap explains in “The Invitation to the Jellicle Ball”: the cats will compete and Old Deuteronomy will appear and select one of the cats to be sent up to the Heaviside Layer and be reborn and given a new life – this is known as the Jellicle choice.
Victoria asks him how the cats compete, and Munkostrap says they need to sing a song. He takes her into a house to show her one of the first cats competing – Jennyanydots (Rebel Wilson), a fat tabby who lives in a home being lazy by day, but as she explains in “The Old Gumbie Cat”, by night she makes the mice and cockroaches help clean the home. She wants a new life to fight off the boredom of this one. The next competitor, Rum Tum Tugger (Jason Derulo), arrives with panache. The Cats sing “Rum Tum Tugger” all about him and his rebellious stylings, and he leads the cats to break into a milk bar and drink up.
When his song is done, a dirty, down on their luck cat named Grizabella (Jennifer Hudson) appears, attempting to join the Jellicles. Many of the Jellicles shun her and explain in “Grizabella: The Glamour Cat” that she was once beautiful but left to join the evil Macavity and was shunned. Meanwhile, Macavity (Idris Elba) lures Jennyanydots away from the group and magically disappears her away.
Bustopher Jones (James Corden), a large fat cat arrives and takes the Jellicle cats dumpster diving for food in “Bustopher Jones: The Cat About Town”. Macavity appears and lures Bustopher with more food, which only tricks Bustopher into falling down a large chute. He and Jennyanydots are tied up on a boat in the middle of the Thames river, guarded by Captain Growltiger (Ray Winstone),
Meanwhile, the cats flee, and Victoria loses the Jellicles and winds up meeting mischievous cat burglars Mungojerrie and Rumpleteezer (Danny Collins and Naoimh Morgan), who sing “Mungojerrie and Rumpleteezer” and break into and burgle a house, which Victoria joins them during. When a vase gets knocked over, they leave Victoria trapped behind with a dog coming to get her. Mr. Mistoffelees, who took a romantic liking to Victoria, arrives and helps her escape, telling her he’d been looking everywhere for her.
They reunite with the Jellicles, and Munkostrap sings “Old Deuteronomy”, about the history of the cat who has lived many lives as she (Judi Dench) emerges from the mist and joins in the song. With Old Deuteronomy there, the time has come for the Jellicle Ball, and the cats enter an old theater and have a massive dance number. Grizabella watches from outside, longing to come in, and Victoria goes out and sings “Beautiful Ghosts”, telling Grizabella that at least she has something – her memories or “beautiful ghosts”. Old Deuteronomy sees this and tells Victoria she is on the path to becoming a Jellicle.
The next contestant is Gus the theater cat (Ian McKellen), who sings his song “Gus the Theater Cat” about how he accidentally became a star of the stage in his youth but is now very old. Mr. Mistoffelees, who performs magic, is a fan and backs up his performance. After, a fan asks Gus to sign an autograph, but it turns out to be Macavity, who kidnaps Gus too. The next cat is Skimbleshanks, who sings in “Skimbleshanks: The Railway Cat” that he is the railway cat and that the train only operates due to his assistance – he too is kidnapped by Macavity.
Suddenly Bombalurina (Taylor Swift) appears above the Jellicle cats and douses them in catnip, lulling them. She sings “Macavity”, explaining how Macavity is the master criminal that has baffled Scotland Yard. Mungojerrie and Rumpleteezer help her subdue the Jellicle cats, and Macavity finally arrives. He tells Old Deuteronomy that since he has removed all the other competitors, she must choose him for the Jellicle choice, and she refuses. He then magically kidnaps her back to his boat, where all the other captured Jellicles are tied up. He begins to force her to walk the plank.
The Jellicles are at a loss, with no way to get Old Deuteronomy back. Victoria urges Mr. Mistoffelees to use his magic, which he very anxiously worries won’t work as he sings “Mr. Mistoffelees”, trying repeatedly to bring Old Deuteronomy back to the theater. The other cats join in singing and encouraging him, and finally, it works. The other captured Jellicles manage to defeat their captors and escape as well.
Grizabella comes back, only for some of the Jellicles to again jeer her to leave, but Victoria beckons her in. Grizabella passionately sings “Memory”, about how her life has become what is has been. The cats are amazed, and Old Deuteronomy names her the Jellicle choice. The cats sing “The Journey to the Heaviside Layer” as Grizabella enters a chandelier that rises and rises until it turns out to be a hot air balloon, which she begins riding into the sky. Macavity leaps out onto a string hanging down, attempting to climb the balloon, but soon falls, and Grizabella goes onward in peace.
The sun rises as the cats watch her go, and Old Deuteronomy addresses the audience and sings “The Ad-dressing of the Cats”, explaining who cats really are and how they should be treated. Mr. Mistoffelees and Victoria have a tender moment, and then Victoria is alone with Old Deuteronomy, who tells her she is a Jellicle cat. Grizabella enters the clouds, entering her new life.