Continuity mistake: In the final scene where Roxie and Velma are dancing in the concert hall, Roxie is on the right and Velma is on the left. They then turn around, and from behind (same point of view as before) they're suddenly the other way around.
Factual error: In the scene where Roxie is placed in the "paddy wagon" to be taken to Cook County Jail, the prosecutor refers to himself as District Attorney Harrison. However, the court system in Illinois doesn't have district attorneys; rather, they have state's attorneys. The original play by Maureen Watkins correctly calls him a state's attorney.
Factual error: When Mr. Flynn is in the restaurant talking about the latest socialite arrested for triple homicide, he briefly uses a telephone their waiter provides. According to an antique phone collector's association, there are many errors between the phone and the time period. First of all, that phone's design was from the Bell Tel. Co., and wasn't manufactured until about 1930. Secondly, even if the movie was set in late 1929, the phone has a handset didn't exist until 1937. Thirdly, the phone is brass-plated with an ivory handset; This colour combo was called the "Imperial", and was introduced to celebrate the 75th Anniversary of Bell Tel. Co. in 1951, and was certainly not available in the 20s.
Continuity mistake: When Roxie is about to fire Billy, there is a close-up of her telling him off, and you can see some loose blonde hairs falling out of her hairstyle. In the next close-up they are gone, and in the next one they're back again.
Continuity mistake: When Velma is dancing and singing for Roxie after making her the offer to replace her sister, during the first half she has an obvious run in her right stocking and a hole about the size of a quarter over her knee. When she tells Roxie the second half is better and finishes her number, the run has disappeared.
Continuity mistake: During the Cell Block Tango, 'Pop' dances with her partner while she sings. When she says "not chewing, popping!", she turns her head sharply and some of her hair lands on her partners hat. When she says, "You pop that gum," she moves and the hair falls off, but in the close up, it is on his hat again in the same position.
Continuity mistake: At the very start of the Nowadays/Hot Honey Rag Medley Title song, where both Velma and Roxie are facing away from the audience, Velma's arm changes position between shots, from being at her side, to on her hip, and back to her side again.
Continuity mistake: In the scene near the end where Roxy is auditioning she gets off the stage and there is a cleaner in the background sweeping. In the next shot the cleaner is right back where he started.
Continuity mistake: Just before Kitty Baxter shoots the 2nd woman sleeping with her husband, she gets a 2-handed grip on the gun. But in the next shot, she is holding the gun 1-handed and once again gets a 2-handed grip.
Continuity mistake: During John C. Reilly's number "Mr. Cellophane", the spotlight angle switches between shots from directly over his head, to in front of him.
Factual error: The innocent murderess, Katalin Hunyák, is supposed to be Hungarian. Nevertheless, in Cell Block Tango, she tells her story with a very heavy Russian accent. And when Billy passes by, she begs for help in Russian ("Pozhaluysta" - "Please").
Continuity mistake: In the final scene when Velma and Roxie are performing, there is lipstick on Roxie's teeth. In the next shot it has disappeared.
Factual error: As Roxie is being escorted into the murderers' row, Mama and Roxie pass Velma's cell. The dollar Velma gives Mama is a modern one.
Continuity mistake: After Roxie shoots Fred Casely, a photographer takes a picture of the body and in the flash from the camera, you can see Fred's eyes are closed and his head is facing straight up. After Roxie's 'Funny Honey' number, the attorney interrogates her and uncovers the body for a neighbor to identify it. When he does this, you can see that Fred's eyes are open and his head is tilted to the side.
Continuity mistake: Near the end of the movie, after Roxie's audition, Velma is pitching her act again when Roxie puts on her coat and buttons it. The camera cuts back to Velma for a minute, then when it cuts back to Roxie her coat is unbuttoned, then seconds later she is walking through a door and her coat is buttoned again.
Continuity mistake: In the scene in which Roxie shoots her lover, he looks into her mirror whilst putting on his tie. He ties it, then puts down his collar. He turns away from the mirror and there's a shot of his back. His collar is up again.
Continuity mistake: In Roxie's first press conference, in certain shots you can see a bit of misting. In others you don't. This suggests that the scene was shot over several days or at different times of the day.
Revealing mistake: If you look closely at Billy Flynn in the musical number "All I Care About is Love", right at the end when he takes off the boxers, you can see that he is wearing underwear underneath them.
Continuity mistake: In the final dance scene with Velma at the Chicago Theater, Roxie's shoes change between the early shots and later ones.
Revealing mistake: In the final dance sequence of The Cell Block Tango, watch Liz (Pop). When everyone else high-kicks, she only kicks out.
Continuity mistake: In the final dance scene, there are supports on the ground for the machine guns when Roxie and Velma are not holding the guns. These supports disappear when Roxie and Velma are holding the guns.
Continuity mistake: When posing for the photographers at Roxie's trial, whenever we see Billy and Roxie from the front, Billy has his arm all the way around Roxie with his hand resting on her stomach. Yet whenever we see them from behind, his hand is resting in the middle of her back.
Continuity mistake: In the scene where Roxie gives Velma her laundry the money in Velma's top moves from hardly seen to almost all the way out.
Continuity mistake: At Roxie's trial when Billy is examining Amos and talking about Roxie's baby, during the close-ups of Amos, the camera goes to Billy when he's asking a question and Amos when he's answering a question. When Billy is ranting about Amos not even asking Roxie if he was the father, during the shots of Amos, Billy is MUCH closer to the witness stand than when the camera goes to his shots.