Late on Christmas Eve night, a boy who doubts the existence of Santa Claus lies in bed hoping to hear the sound of reindeer bells from Santa's sleigh. When he hears a steam engine's roar and whistle outside his window, the conductor invites him on board to take an extraordinary journey to the North Pole with many other pajama-clad children. There, he receives a gift only those who still believe in Santa can experience.

Jack Skellington is the King of Halloween. He becomes bored with the same routine every year. He decides to take a walk in the woods. There, he discovered a door leading to Christmastown and decides to spread Christmas joy to the world. When he is back in Halloweentown he shows his friends what Christmas is like, and he suggests doing Christmas this year instead. But things do not go as planned when Oogie Boogie, an evil gambling boogey man, plots...

Scott Calvin has been Santa Claus for the past eight years, and his elves consider him the best ever. But Santa's world is turned upside down when his son gets on the naughty list, and if Scott doesn't marry soon, he'll stop being Santa forever.