Deliberate mistake: To make Jim Braddock look more heroic, Max Baer is portrayed as being very mean and hateful. In fact, the real Max Baer was an extremely pleasant man who was devastated when Frankie Campbell died after fighting him. Many boxing historians and sportswriters have complained about this inaccurate depiction of Baer.
Continuity mistake: When Mae is at the sink washing dishes and, behind her, Braddock is teaching his kids how to box, Mae turns around and emotionally yells, "No boxing in the house!", the strap on the apron she is wearing is twisted. They cut away and in the next shot the strap is no longer twisted.
Other mistake: During the Baer and Braddock fight, when the camera angle is from far away, you can see that Braddock is not actually connecting with his punches on Baer. Yet Baer still reacts like he's been hit. This also true with Baer hitting Braddock when the camera is showing the fight from far away in the stands.
Factual error: Jim's manager drives away after asking him to consider another fight. In the reflection of his windshield you can see palm trees blowing in the wind, an odd sight for New Jersey.
Continuity mistake: When Gould comes to tell Braddock that he got him a fight with Corn Griffin, they are standing in the open behind all of the apartments. In the background you can see an African American boy carrying a bucket of something through an alley. The camera angle changes and you see the boy start to walk up the alley again. It's the same shot, and it's right near the part where Gould tells Braddock that he will get $250 for the fight.
Continuity mistake: During the Lasky/Braddock fight, Braddock gets a cut on the right side of his face right by his eye. It lines up almost perfectly horizontal with the middle of his right eye. The next time we see him after the fight, when he is returning the relief money, the cut has moved up higher on his right side of his face.
Visible crew/equipment: If you look very closely when Braddock makes his son Jay return the salami to the Butchers, you can see the camera in the window of the butcher shop. It is more evident when they walk out of the store.
Continuity mistake: When Braddock is fighting Art Lasky, his face gets punched so hard that his mouth piece goes flying out of his mouth and hits the ground. There are drops of spit from the mouth piece on the ground that surround the mouth piece. However, about 10 seconds later when Braddock picks up the mouth piece, the drops of spit on the ground are gone. There is no way the spit would have dried that fast, no matter how hot the floor would have been with the lights on it.
Continuity mistake: The first time we see the relief office, it says, "Emergency Relief Aid." The next time we see the wall (when Braddock returns the money), it says, "Make sure that you have all of your forms filled out completely."
Continuity mistake: When Joe and Braddock are in the locker room, after he has just fought Corn Griffin, Joe is all excited and he starts opening locker doors to find his jacket. He finds his jacket and closes the locker door, but when the shot changes the locker door is now open again.
Factual error: In the scene prior to the Braddock/Baer fight, when Jim's wife Mae comes into the locker room and gives him the heartfelt spiel about being behind him in this fight after all, she leaves the room and as she leaves Jim, Russell Crowe, is standing there in a white "wife beater" tank top. It is a new one with a screened on tag by either Fruit of the Loom or Hanes. Screened-on tag tees didn't come about until the last few years.
Other mistake: During the opening scene of the movie with one of Braddock's boxing matches, he wins midway through the 2nd round. Yet, the clock on the wall behind the ring is straight-up, indicating that the clock had not even been started.