Revealing mistake: In the first scene, when the IRA fighters in the burning building surrender, the absolutely smoke-free fires in the windows look like cosy, gas-fuelled fireplaces. (00:03:50)
Continuity mistake: After Kitty wakes up Michael and Harry, the way she holds the water can changes between shots. (00:14:05)
Continuity mistake: When Michael Collins and his men raid the police station they throw torches on the roof. A second later the whole building is on fire, and the policemen run out coughing and gasping for air. However, when the IRA people go in to get the police guns the air is quite breathable. (00:15:25)
Suggested correction: When the policemen exited the building, they opened the doors, which let much of the smoke out, allowing the IRA men to enter without succumbing to smoke inhalation.
Other mistake: After the attack on the police station we see a train passing by in front of the fire. The shiny train reflects the flames in a way that could only be caused by another fire for which there is no evidence. (00:16:20)
Suggested correction: We do not know that the IRA didn't set another fire. They may well have, but it wasn't shown. As there is another fire reflected on the train, then it must have been set, but the viewer was not shown the details.
Continuity mistake: When Michael Collins searches through the files in the castle he takes the only photograph from his file and shows it later to Harry Boland. But when the file is given to Soames, the photograph is back in. (00:30:30 - 00:52:15)
Suggested correction: The British authorities in Dublin Castle were capable of making copies of photographs and reproducing them. They would not have had only one copy.
Continuity mistake: When Michael Collins announces to his men that all collaborators will be shot his hair changes from messy to perfectly combed between shots. (00:30:50)
Continuity mistake: Early in the film, Michael talks to Harry Boland on a boat. During this scene, a cigarette appears in Boland's mouth that was not in the previous shot. (00:40:40)
Revealing mistake: There's one head of police who, during his short stint in Dublin, pledges to introduce 'Belfast efficiency'. Shortly after that he is killed by a car bomb. However, when the bomb goes off there's a split-second shot where the car is empty although three men had just gotten in, and the driver who was starting the car is a rather crude dummy. (00:46:05)
Continuity mistake: There's one scene where Michael Collins talks to Ned Broy standing on a small pedestrian bridge while a train passes overhead. From the railing construction you can tell that the close-up was taken at a different place than the wide shot. (00:51:05)
Continuity mistake: When Ned Broy comes to Vaughan's the night he gets killed the receptionist is sleeping on the counter. He wakes up a few minutes later when the hotel gets raided, and next to him there is a bell that hasn't been there before. (00:58:50)
Revealing mistake: When Soames gets shot through a folding screen huge fireballs erupt from his body when the bullets hit him. (01:03:30)
Factual error: During the Croke Park massacre, the British never rolled an armored car onto the Gaelic football field, as depicted in the film. It remained outside the gates. (01:05:20)
Continuity mistake: When the armoured car interrupts the ball game a player scores a goal to mock the attackers. The player who receives the ovations and gets shot in return is not the one who scored the goal, and there are bullet holes in his tricot even before he gets hit. (01:06:05)
Revealing mistake: After the attack on the ball game Michael Collins visits a morgue. The corpse that is lying next to him is breathing quite visibly. (01:07:20)
Continuity mistake: When DeValera returns from America Joe O'Reilly hands him a paper with the news. It is folded in a way that shows cover outside, but when DeValera opens it the crease is the other way. (01:08:45)
Continuity mistake: When Michael Collins joins the first cabinet meeting after DeValera's return he puts a briefcase on the table in front of him and takes out some papers. When the camera angle changes the briefcase is gone. (01:09:45)
Other mistake: When Kitty reads Michael's letter from England to Harry, there's some strange smoke arising from behind their chairs. (01:19:40)
Revealing mistake: When Liam Neeson is on the boat on his return from England there is a shot of the water and part of the boat where you can see a modern CCTV camera on the side of one of the masts - rather advanced for the time the film was set. (01:21:20)
Factual error: The Lee Enfield rifle is chambered by singular repetitions with a bolt action. When Collins' wayward friend is shot in the water, the rifle shots are rapid semi-automatic fire.
Factual error: During one of the cabinet meetings, one of the members says Collins' brief is Minister for Intelligence, but he was actually Minister of Finance. He was, however, the IRA's Director Of Intelligence.
