In the early 1930s, four disparate lives will come together to create one of racing history's greatest legends. Charles Howard, a self-made millionaire, copes with the accidental death of his young son by immersing himself in racing. He meets Tom Smith, a seemingly washed-up race horse trainer unable to adapt to a modern world. Nevertheless, Howard is impressed by Smith and his abilities, and he hires him as head trainer for his racing stable. While scouting for new horses, Smith spots Seabiscuit, a small, gangly colt who, despite being the grandson of the legendary champion, Man O'War, has descended to the lowest ranks of the claiming race circuit. But Smith sees potential in the horse and convinces a skeptical Howard to buy him.
A defiant and temperamental Seabiscuit refuses to let anyone ride him until one day Red Pollard, a down-on-his-luck jockey, wanders into the Howard Stable. Like Smith, Red has a gift working with difficult horses. He and Seabiscuit immediately take to each other, and Smith hires him. Under Tom’s training, Red and Seabiscuit begin winning races and breaking records.
Seabiscuit becomes a national hero to a Depression-weary America. To prove Seabiscuit a true champion, however, Howard proposes a match race against War Admiral, the greatest race horse of the time. War Admiral’s owner, Samuel Riddle, considers Seabiscuit inferior and is uninterested in a match race. But after intense public pressure, he finally agrees. Just before the big race, Red Pollard suffers a horrendous riding accident that nearly severs his leg. His long-time friend and jockey legend, George "The Iceman" Woolfe replaces Red in the match race.