In the charming town of Ridgefield, New Jersey in 1985, Robbie Hart, known as the go-to wedding singer, is eagerly anticipating his own marriage to fiancée Linda. However, his life takes an unexpected turn when he meets Julia Sullivan, a delightful waitress at the reception hall where he performs. Engaged to Glenn Gulia, a business-savvy and cold-hearted bond investor, Julia finds herself stalled on setting a wedding date. Ever the romantic, Robbie promises to sing at her wedding.

As Robbie’s own wedding day draws near, a crushing revelation from his sister, Kate, shatters his dreams: Linda is no longer interested in tying the knot. Heartbreakingly, Linda confesses that she was more attracted to Robbie’s ambitions of being a rockstar than the reality of life as a wedding singer. Devastated, Robbie sinks into a deep depression, causing strains in his relationships with friends and family.

With encouragement from his loyal best friend Sammy, Robbie begrudgingly goes back to work but struggles to regain his usual spark. Doubting his capabilities, he breaks his promise to Julia, thinking of abandoning the wedding gig entirely. Yet, Julia’s kind nature and their budding friendship start to awaken something lost within him.

As Robbie helps plan the wedding of Glenn and Julia, he becomes more involved in her life. A double date reveals Glenn’s infidelities, making Julia doubt her forthcoming nuptials. Confiding in her mother, she admits her waning passion for Glenn and growing feelings for Robbie. Despite grappling with his own heartache, Robbie attempts to mirror Sammy’s approach to relationships, only to realize that he desires something real with Julia.

In a pivotal moment, Robbie arrives on Julia’s doorstep ready to express his feelings, only to find her in a wedding dress, dreaming of a future with him—unaware of his presence. Consumed by jealousy and heartache, Robbie turns to alcohol. A confrontation with Glenn at a bachelor party leads to a physical altercation, deepening Robbie’s despair. The next morning, reality strikes when Linda introduces herself to Julia as Robbie’s fiancée, which shocks both women and initiates Glenn’s impulsive plan to elope in Las Vegas.

Meanwhile, following a night of recklessness, Robbie emerges with clarity. His heartbreak over Linda becomes a platform for newfound appreciation for Julia’s depth, prompting him to end things with Linda. At Rosie’s 50th wedding anniversary, Robbie receives crucial advice about seizing the moment. With renewed focus, he realizes he wants to grow old with Julia.

Just as he gathers his resolve, he learns of Julia’s airport encounter with Linda, and without hesitation, he secures a first-class ticket to Las Vegas to intervene. On the flight, Robbie shares his story with fellow passengers, including music icon Billy Idol, who inspires him further. Knowing Julia and Glenn are on board stirs his determination.

With Billy’s assistance, Robbie takes to the cabin’s loudspeaker, passionately singing his original song “Grow Old With You” for Julia. The heartfelt performance overwhelms everyone, and as Glenn attempts to confront Robbie, he finds help in the flight crew and Billy, who ensure Glenn is temporarily detained.

Once they arrive, Robbie and Julia declare their love and share a tender kiss, solidifying their future together. Impressed by Robbie’s talent, Billy offers to introduce him to recording executives, heralding a new beginning in his life. Ultimately, Robbie and Julia marry, surrounded by their friends and family, with David Veltri strumming the guitar, marking the start of their lifelong journey together.