In the charming village of Greendale, located in the northern part of England, Patrick "Pat" Clifton, lovingly referred to as "Postman Pat", has spent years faithfully delivering letters and spreading happiness among the locals. His long-awaited honeymoon with his beloved wife Sara is finally on the horizon—a romantic trip to Italy he's been dreaming about for what seems like ages. Just when Pat is poised to realize this dream, harsh truths from his work at the Special Delivery Service (SDS) throw a wrench into his plans. The newly appointed boss, Edwin Carbunkle, has eliminated all bonuses, leaving Pat's financial situation in tatters.
Returning home to share the disappointing news with Sara, he stumbles upon an unexpected surprise; his young son Julian is captivated by an episode of the popular talent show, You're the One, hosted by the charismatic Simon Cowbell. Luck is on Pat's side because the next round of auditions is set to take place in Greendale, with the grand prize being a trip to Italy—exactly what Pat was about to abandon. But the prize doesn’t stop there; the winner will also receive a coveted recording contract, an opportunity that could propel Pat's life into a realm he never imagined.
Driven by the prospect of this life-changing reward, Pat decides to seize the moment and audition for the show. To everyone's shock, his hidden singing talent shines brightly, propelling him to the finals against a formidable rival, Josh. Yet, with triumph comes a complication: Pat soon realizes his manager Wilf is more focused on winning at any cost than on supporting Pat's authentic love for music.
Meanwhile, the executives at SDS, including Mr. Brown and Edwin Carbunkle, closely monitor Pat's progress on the show, impressed by his burgeoning fame. They envision using this newfound celebrity to launch a publicity campaign featuring Pat as the star of their new television series. To add to the absurdity, Pat is set to be replaced by a robotic duplicate known as the "Patbot 3000" while he competes on the show, designed to fulfill his postal duties alongside its counterpart, the "Jessbot."
During Pat's absence, the residents of Greendale begin to sense something amiss as the Patbot, responsible for delivering mail on Pat's behalf, exhibits odd behavior. This development raises suspicions among the villagers, particularly Sara and Julian, who can’t help but wonder if Pat has somehow changed for the worse. Meanwhile, Ben Taylor, the former manager at SDS, finds himself unjustly fired by Carbunkle, his paranoia spurred by the belief that Pat no longer wishes for him to be around, completely unaware that the real Pat is actually being replaced by a robot.
Wilf, always the trickster, tries to sabotage Pat's efforts, but his schemes only lead to unexpected consequences. As concerns mount among Pat's family and friends regarding his behavior, Pat himself struggles with guilt for entering the competition. His attempts to explain his true motivations to Sara fall flat, leaving him fearful that he may have damaged his precious relationships.
Everything comes to a head when Ben and Jess discover a startling truth: there seems to be more than one Pat. As Edwin Carbunkle's nefarious intentions unravel, it becomes evident that this contest is part of a grander scheme to create an army of robotic duplicates aimed at world domination.
Empowered by this knowledge, Sara takes action, rallying the townsfolk to inform them about Carbunkle's evil plans and to reassure them that the real Pat remains unchanged at heart. Together, the people of Greendale join forces to support Pat in his quest, while Jess—having secretly hidden aboard one of the SDS's helicopter replicas—manages to reach Pat during his performance, aiding his escape from the clutches of a rogue Patbot and Carbunkle.
As Pat realizes he has become a mere pawn in Carbunkle's game, he faces a thrilling confrontation in a dressing room, grappling with the blurred lines of his so-called fame. Carbunkle’s ultimate aim becomes clear; he wishes to replace Pat with a battalion of Patbots meant to win over the public's affection. Equipped with Jess’s loyalty, Pat must deploy all his cleverness to outsmart the Patbots and the Jessbot, ultimately carving his path into the theater where he will confront Carbunkle in a battle for dominance.
During the climactic performance, a Patbot takes the spotlight disguised as its creator, with the audience oblivious to the deception. However, Wilf's sharp instincts catch the performance's fakeness as he wields his trusty magnet to expose the mechanical impersonator. The real Pat dramatically enters, delivering a heartfelt discourse on the significance of relationships and the need to cherish those we hold dear. But just as everything appears to settle, Carbunkle initiates his nefarious plan, unleashing a trio of menacing Patbots determined to obliterate Pat, Simon, and Mr. Brown.
In a bold move, Josh commandeers Carbunkle's phone, using it to deactivate the robotic attackers before they can cause havoc. Unbeknownst to Pat and his companions, their loved ones from Greendale are on the verge of arriving, ready to add chaos to the whirlwind event.
Ultimately, after Mr. Brown's audacious choice to oust Carbunkle and have him apprehended, normalcy returns to the performance. As Pat shares his true motivation for entering the contest—the desire to secure flight tickets for his dream honeymoon with Sara—he remains blissfully unaware that his wife has been privy to every word he’s spoken.
Sara’s emphatic call of Pat’s name stuns the audience, unveiling her awareness of Carbunkle’s treachery and Pat's genuine intentions. With Sara’s forgiveness firmly established, Pat opts to alter his act, resulting in a jubilant, heartwarming performance that unites everyone present.
As the curtain falls on this enchanting spectacle, Pat and Mr. Brown harmonize a rousing rendition of Signed, Sealed, Delivered (I'm Yours), supported by Josh, Wilf, and the residents of Greendale lending their voices to the collective chorus. Sara steps into the spotlight beside Pat, and together they triumphantly accept the grand prize—a romantic Italian getaway. Demonstrating remarkable generosity, they graciously choose to pass the recording contract to Josh, a decision that brings great joy to Wilf, as all grievances are laid to rest.
