Vince Everett (Elvis Presley) is a 19-year-old construction worker who, after a long days work, goes to a local bar for a beer when he has an altercation with a drunk and belligerent man. A bar-room brawl breaks out where Vince punches the drunk and weak man so much that he accidently kills him.
Vince is arrested and sentenced to between one and ten years in the state penitentiary for manslaughter. His cellmate is a middle-aged, washed-up country and western singer named Hunk Houghton (Mickey Shaughnessy) serving time for armed robbery and has been at the prison for eight years now. Hunt starts teaching Vince to play the guitar after hearing Vince sing and strum Hunk's guitar. Hunk convinces Vince to participate in an upcoming inmate show, which is broadcast on nationwide television. Vince receives numerous fan letters as a result, but Hunk ensures they are not delivered to Vince. Hunk then convinces Vince to sign a contract to become equal partners in his act.
One day, during an inmate riot in the mess hall, a guard shoves Vince, who retaliates by striking the guard. As a result, the warden orders Vince to be lashed with a whip. Afterwards, it was discovered that Hunk attempted to bribe the guards to drop the punishment, but to no avail.
After serving 14 months of his sentence, Vince is paroled from prison for good behavior where, shortly before leaving, the warden gives Vince his fan mail which makes Vince realize that Hunk tried to shield him from his fans. Hunk promises Vince a singing job at a nightclub owned by a friend. Vince is surprised when the club owner denies him a job as a singer but offers him a job as a busboy. During this time, Vince meets Peggy Van Alden (Judy Tyler), a young woman that frequents the club and who works as a promoter for pop singer Mickey Alba.
Vince goes on stage when the house band takes a break, and starts to sing "Young and Beautiful", but becomes enraged by a customer who is paying no attention and laughing. Vince smashes his guitar and leaves the club. Peggy follows Vince back to his small apartment and persuades him to record a demo so that he can listen to himself.
Vince records "Don't Leave Me Now" at a recording studio, which Peggy takes to Geneva Records. Unimpressed, the manager agrees to play the tape for his boss in New York. The next day, Peggy informs Vince that the song has been sold. She then takes him to a party at her parents' home, but Vince offends a guest he mistakenly believes is belittling him and leaves. Angry and offended, Peggy confronts Vince, who kisses her.
Some weeks later, Vince and Peggy go to buy Vince's single, but are shocked to discover Mickey Alba's recording has been released instead. Vince storms into the label's office and punches the manager. To avoid being deceived, Vince suggests that he and Peggy should form their own label, which they do. The name it Laurel Records and hire an attorney, Mr. Shores (Vaughn Taylor) to give them advice. Vince records "Treat Me Nice", and begins pitching it but it is universally rejected. Peggy convinces her friend, disc jockey Teddy Talbot (Dean Jones) to air the song in exchange for a date, and it becomes an immediate hit.
Later that evening, Vince asks Peggy out to celebrate, but is disappointed when he learns that she has accepted a dinner date with Teddy. Due to Vince's growing popularity, he is invited to New York to appear on a TV variety show to sing his song. During a party, Hunk visits him after being paroled and persuades Vince to give him a spot on the upcoming show. At the show, Vince rehearses "Jailhouse Rock" in a stylized cell block. Hunk's number is cut because of his outdated music style. Afterward, Vince informs Hunk that according to his lawyer, the contract they signed in prison is worthless. Vince offers Hunk instead a fee of 10% of his earnings, which Hunk accepts.
Within a few months, Vince is a star. Peggy is no longer on speaking terms with him, as his success has made him arrogant and self-absorbed. Vince travels to Hollywood where he signs a movie deal with Climax Studios to record the soundtrack as well as star in an upcoming film. The studio head asks him to spend the day with Sherry Wilson (Jennifer Holden), the studio's new leading lady, for publicity purposes. The actress is less than thrilled with her co-star at first, but eventually falls in love with Vince.
Meanwhile, Hunk begins to grow tired of Vince's self-centered attitude. When Peggy shows up unexpectedly at a party at Vince's newly leased Hollywood home, Vince is happy to see her but becomes upset when she says the purpose of her visit is to talk about business. Mr. Shores approaches Vince with an offer from Geneva Records to purchase Laurel Records and sign him to a rich contract.
On the closing day of his film being wrapped up, Vince tells Peggy about the offer he received. Peggy refuses to sell out to Geneva Records, but Vince announces that he will close the deal since he owns a controlling interest in the label, which upsets Peggy. Enraged by Vince's attitude, Hunk provokes Vince, who refuses to fight back. Hunk hits Vince in the throat, endangering his singing ability. Vince is rushed to a hospital. Vince forgives Hunk and realizes he loves Peggy and she loves him.
A few weeks later, Vince's doctor declares that his vocal cords are fully recovered, but Vince is worried that his voice might have been affected. He sings "Young and Beautiful" to Peggy, which reassures him that his fears are unfounded.