Starting in a flashback on the night of Christmas Eve, a boy starts to become skeptical of the existence of Santa Claus. Struggling to fall asleep, he witnesses a steam locomotive arrives on the street and goes outside to examine it, ripping a hole in his dressing gown pocket on the way. The conductor introduces the train as the Polar Express, which was on its way to the North Pole. Initially reluctant, the boy jumps aboard as the train departs.
In a passenger car, he meets a spirited girl and a smart know-it-all boy. The train picks up a boy named Billy, who also declines to board, but changes his mind, and the boy pulls the emergency brake to allow Billy to board, much to the conductor's annoyance. As Billy sits alone in the train's observation car, hot chocolate is served in the passenger car, and the girl stows away a cup for Billy. As she and the conductor cross to the dining car, the boy notices that she left her unpunched ticket but loses hold of the ticket between the cars when he attempts to return it, and the ticket ends up blowing away into the wilderness where it is played with by animals. The ticket reenters the passenger car, but not before the conductor notices its absence and escorts the girl back to the rear car.
When the know-it-all boy claims that the conductor will throw the girl from the train, the boy recovers the ticket and dashes to the dining car in search of the conductor, climbing onto the roof. He meets a hobo camping on the roof, who offers him coffee and discusses the existence of Santa Claus and ghosts. The hobo skis with the boy along the tops of the cars toward the coal tender, where the hobo disappears right at Flat Top Tunnel.[a]
In the locomotive's cab, the boy discovers that the girl has been made to supervise driving the train while the crew Steamer and Smokey replace the headlight. The boy applies the brakes and the train stops coming across a herd of caribou blocking the tracks. The conductor pulls Smokey's beard, causing him to let out animal-like noises, and the caribou herd clears the tracks.
The train continues on at extreme speed, and the throttle's split pin (cotter pin) shears off; causing the train to accelerate uncontrollably to Glacier Gulch, down a 179-degree grade, and onto a frozen lake. Smokey uses his hairpin to repair the throttle as the train drifts across the ice to realign with the tracks moments before the ice breaks. The boy returns the girl's ticket for the conductor to punch, and as the three return to the passenger car, the Hobo uses a Scrooge puppet, taunting the boy and calling him a doubter.
The train arrives at the North Pole, where the conductor announces that one of the passengers will be chosen to receive the first gift of Christmas from Santa himself. Discovering Billy still alone in the observation car, the girl and boy persuade him to come along, but the boy accidentally uncouples the car; sending it back along the line, down a turnaround, through a tunnel where the wheels spark, and onto a railway turntable in Santa's workshop. The children make their way through an elf command center and a gift sorting office before sliding down a massive slide that leads them to a funnel before being dumped into a giant sack of presents, where they discover that the know-it-all has stowed away. The elves escort them out before Santa and his reindeer arrive.
A bell flies loose from the galloping reindeer's reins; the boy initially cannot hear it ring, until he finds it within himself to believe. He shows the bell to Santa, who selects him to receive the first gift of Christmas. Santa agrees to let him keep the bell, and the boy places it in his robe pocket.
The rear car is returned to the train as the children board to return home, but the boy discovers that he lost the bell through the hole in his pocket. He returns home and awakens on Christmas morning to find a present containing his lost bell. He and his younger sister Sarah joyfully ring the bell, while their parents, not believing in Santa, don't hear the bell and say that the bell is broken.
The boy reflects on his friends and sister eventually growing deaf to the bell over the years as their belief faded. However, despite his now old age, the bell still rings for him, as it does "for all who truly believe".
Tom Hanks as Hero Boy (motion-capture), Hero Boy's father, Conductor, Hobo, Scrooge puppet, Santa Claus, and the Narrator
Daryl Sabara as Hero Boy (voice)
Josh Hutcherson as Hero Boy (additional motion-capture)
Leslie Zemeckis as Sister Sarah (motion-capture) and Hero Boy's mother
Isabella Peregrina as Sister Sarah (voice)
Ashly Holloway as Sister Sarah (additional motion-capture)
Eddie Deezen as Know-It-All
Jimmy Pinchak as Know-It-All (additional motion-capture)
Nona Gaye as Hero Girl
Chantel Valdivieso as Hero Girl (additional motion-capture)
Meagan Moore as Hero Girl (singing voice)
Tinashe as Hero Girl (motion-capture model)
Peter Scolari as Billy the Lonely Boy (motion-capture)
Hayden McFarland as Billy the Lonely Boy (additional motion-capture)
Jimmy Bennett as Billy the Lonely Boy (voice)
Matthew Hall as Billy the Lonely Boy (singing voice)
Dylan Cash as Boy on Train (voice)
Brendan King and Andy Pellick as Pastry Chefs
Josh Eli, Rolandas Hendricks, Jon Scott, Sean Scott, Mark Mendonca, Mark Goodman, Gregory Gast, and Gordon Hart as Waiters
Michael Jeter as Smokey and Steamer (motion-capture)
André Sogliuzzo as Smokey and Steamer (voice)
Chris Coppola as Gus the Toothless Boy and an Elf
Connor Matheus as Toothless Boy (additional motion-capture)
Julene Renee as Red Head Girl and an Elf
Phil Fondacaro, Debbie Lee Carrington, Mark Povinelli, and Ed Gale as Elves
Charles Fleischer as Elf General
Steven Tyler as Elf Lieutenant and Elf Singer
based on the 1985 children's book of the same name by Chris Van Allsburg
listed in the 2006 Guinness World Records as the first all-digital capture film.