Continuity mistake: Toward the end, Thénardier is being dragged down the stairs after Marius took back the gold ring Thénardier stole off his unconscious body previously. The gold ring appears and disappears several times as Thénardier is being pulled out of the room, down the stairs, and out the door. At the end, Marius shows the gold ring to Jean Valjean as he is dying, which was last seen on Thénardier's finger as he was being pulled out the door.
Factual error: In the opening sequence, the convicts are located in a dry dock pulling on ropes supposedly connected to a listing ship in the distance. The convicts are standing in 2 to 3 feet of water which would indicate that the dock is "dry" and that the dock gates are closed. The ship will be unable to enter the dock under those circumstances. If the gates were open enough to allow the ship entry there would be 20 to 30 feet of water in the dock and the convicts would need to be up on the top of the dock to achieve their objective.
Continuity mistake: In the scene early in the film, where Valjean is singing in the church (after the police brought him back to the minister for stealing the silver), he has a wound on the right hand side of his head (from being hit by the policeman's stick/truncheon). Depending on the camera angle, the size of the wound and its appearance alters- sometimes it is quite small and flat, other times raised. Also sometimes there is a trickle of blood from it and other times not.
Continuity mistake: In the scene where Eponine (Samantha Barks) sings "On My Own", towards the end of the song, her hands come into shot, they are immaculate and manicured. Immediately after the song, she goes into a building to retrieve Cosette's letter to Marius, whilst holding the letter her hands are filthy with dirt under the nails.
Factual error: When Javert is singing "stars" he is walking a rooftop that appears to be another church across from Notre Dame. The church of Sainte Chapelle is in that direction, but looks nothing like what is depicted in the movie. Later when Javert has his solo on the bridge behind Notre Dame, the building he was standing on earlier should be visible from that angle, but was not included in the background.