Continuity mistake: When Alice wakes up in the shower, in one shot, you can see the shower curtain is not hanging over the edge of the shower. But when it cuts, it is. (00:08:40)
Continuity mistake: When they are entering the entrance to the Queen's chamber, the Medic is carrying a bag as you can see when the door closes. When it cuts from inside the entrance the bag has disappeared. (00:30:50)
Continuity mistake: When Kaplan tells Alice not to listen to the Queen he is carrying the equipment by his right shoulder. When it cuts it has suddenly moved over to his left shoulder. (00:34:45)
Revealing mistake: When Alice hits the first person in a biohazard suit, the padding is visible on the chest section. (01:25:40)
Revealing mistake: When Alice hits the zombie Spence in the head, she misses Spence by a lot. (01:18:50)
Continuity mistake: When Spence has been killed we see the broken monitor which has a white column through the screen, which turns black or white depending on the shot. (01:16:00)
Continuity mistake: When Kaplan is walking through the corridor to get the EMP and head into the Red Queen's chamber, Medic's legs are together. When we see all the power shutting off, her position has changed and now her legs are apart. (00:32:40 - 00:35:50)
Revealing mistake: When Kaplan is trying to turn off the lasers, take note of his keyboard. His fingers aren't touching the keys. (00:31:20)
Continuity mistake: When we see the extreme close up of the robotic arm picking up the blue vial, the grip is uniform and parallel to the edge of the sliver end cap on the vial. When we see the vial a second later, the arm's grip has changed and is no longer parallel or uniform on the vial. (00:02:10)
Continuity mistake: Alice's scar on her left shoulder changes shape and redness throughout the film. (00:09:05 - 01:25:00)
Continuity mistake: When the Red Queen kills all the workers in the main office, the positions and actions of people differ from the video footage to the actual events. (00:06:35)
Continuity mistake: When we see a CGI map of The Hive right before the Laser Room, the 3D thermal camera reveals a very rigidly stood up human body looking through the door's small window. When the camera cuts and we actually see Alice look through the window, she's slightly bent down so her head is on window level since she's taller. It's quite possible the CGI team just didn't spend more time than necessary to move the thermal human model's limbs and kept it in an almost default T-stance position. (00:29:30)
Continuity mistake: The guy states that the room is sealed and his facial expression is one of panic. Camera cuts and now he's facing a different way and his expression has changed completely. (00:05:20)
Continuity mistake: When the elevator starts to drop from floor 10, the floor indicator says 7, but a moment later it counts down from 9. (00:06:05)
Continuity mistake: In the beginning when Alice is wiping the mirror, you can see her mouth is open. When it cuts back to her it is closed. (00:09:00)
Continuity mistake: When Rain is under the train using her flashlight to see if she can see something the hair hanging across her face changes position between the wideshot and the close-up shot. (00:16:00)
Continuity mistake: When the SWAT team arrives at the hive, the open an elevator shaft and one of them lights a flare with 2 hands. As the camera changes, he is now holding it at arm's length and with one hand without enough time to do so. (00:23:05)
Continuity mistake: When Rain tries the door on the train and fails, we see her face and her hair has 2 strands on one side of her face. Camera changes and now she's got 1 strand. (00:16:50)
Continuity mistake: In the laser corridor, the team leader is stood upright when the lights comes on, but as the camera changes to a front view, he is crouched. (00:30:10)
Suggested correction: It's easy to miss, but there is a quick insert-shot in-between these two shots that shows the team leader crouching down suddenly. (The camera is focused on the back of his head as he ducks down suddenly.) It can be seen in this video (https://www.youtube.com/watch?v=rOLe15-5Xhw&t=65s) around the 1-minute mark.
Continuity mistake: When the first laser passes through it hits the one guy in the wrist, however we see him on the floor missing half of his fingers and hand instead. (00:31:30)