Continuity mistake: In the race for the $100,000 purse (that Rosemont wins), just after Seabiscuit takes the lead, there's a closeup of Seabiscuit's head and Pollard's right leg - Pollard is wearing the brace he made later in the movie after his leg was shattered. Obviously, the shot was taken from those filmed for the Santa Anita race later in the film.
Continuity mistake: In Seabiscuit's first race under Pollard, at the start the announcer says, "Pirate Cove breaks first with Geronimo on the outside. Silver Treasure is third followed by Seabiscuit." But when it cuts to Seabiscuit, there are six horses in front of him, placing Seabiscuit seventh. Seabiscuit would have to be barely moving to lose that much ground that fast.
Continuity mistake: In the movie, War Admiral is described as standing 18 hands tall, compared to Seabiscuit's 15.2 hands. Although this is not historically correct (according to contemporary sources, both horses stood around 15.2 hands) the size disparity created by the movie is not carried on in the match race, where the two horses appear to be the same size.
Continuity mistake: In the scene where everyone is waiting for Red to get out of surgery, a nurse walks by with a stethoscope around her neck. This is a mistake for a couple of reasons. Number 1, it is a modern style Littman stethoscope that wasn't used until the 1970's. The old stethoscopes of the 30's look really different than they do now. Also, back then, nurses didn't routinely carry stethoscopes like they do these days to do assessments.
Continuity mistake: When Tick Tock McGlaughlin watches Seabiscuit being prepared for racing again he pretends to be reading a newspaper. When Charles and Tom talk to him he is holding the newspaper open with both hands, but at the end of the conversation he is suddenly holding the folded newspaper in one hand.
Continuity mistake: When Charles gives Red $20 with his left hand he is holding a newspaper under his right arm. The camera angle changes that we see Charles' upper body from behind, he puts his right hand on Red's shoulder, and when we see the whole Charles again the newspaper has disappeared.
Continuity mistake: When Red is telling the new jockey all about Seabiscuit's peculiarities, he tells the jockey not to use the crop on the left because a previous trainer had beaten him on that side. Earlierwhen the horse was working with that trainer, they show him being beaten on the right side.
Continuity mistake: Before the match race between Seabiscuit and War Admiral, Charles and Mr. Riddle take their seats. They exchange a few words, then Riddle turns away to talk to his seat neighbor, but when the camera cuts to Charles we see Riddle in the background still looking at him as he did before.