Continuity: When Hancock puts the woman on the hospital bed near the end of the movie when he walks out he walks into the metal bar holding the window in place and as a result it bends. In the next shot where you see the frame it doesn't even have a scratch let alone being bent.

Visible crew/equipment: When Hancock returns Embrey and his car back to his house just after saving him and then picks up and moves the car onto the drive, you can see the blue crane used in the reflection of the car windscreen.

Other: In the scene where Mary Embrey goes to Hancock's trailer to tell him about their past, Hancock says something to the effect of "sisters don't kiss their brothers the way you kissed me in the kitchen last night." In fact, the night before, they never kiss, they just come real close to kissing before she throws him through the wall.

Other: The locomotive in the train wreck was a low-powered switching engine. Dozens and dozens of rail cars kept piling up, yet that engine would not have been powerful enough to pull such a long train in the first place.

Continuity: When Hancock is being shown the YouTube videos, on the computer the watermark is on the left. but when it's shown on the whole screen, it's on the right.

Continuity: During the battle between John and Mary, a huge storm brews up above and around them. Shots of Ray having a meeting show this storm outside the window. But just before the office is torn open, a close-up of Ray in the office shows a normal, late-day sunny sky, then the wall is ripped open and the gray/blue storm is there again.

Continuity: In the part where Hancock tries to hit Mary Embrey with the pans, she turns around, and there is a shot, showing what Mr. Embrey is doing, and Hancock and Mary in the background. Between these shots, Hancock is holding the pans up and then he's holding them down.

Factual error: When the police are cowering behind their bullet riddled cars, the metal on the bullet holes is bent inwards as if the shots had come from the other direction.

Continuity: (Spoiler Alert) the day after Hancock finds out that Mary also has powers, he stabs her with a large fork with two pointy ends. As expected, they do not puncture her skin. The pointy ends bend toward each other, making a triangle shape. But in the next shot, when Mary snatches it from his hand, the tips are no longer in a triangle shape, just bent the wrong way a little. Mary snatches it away by the handle, so we know that she could not have taken it by the points and bent it.

Continuity: As Hancock enters Ray's house through the hole in the wall, you can see Hancock is not wearing anything around his neck. As this scene progresses, his gold eagle chain is visible at times.

Factual error: In the box Hancock has from attack in the 1930s, it shows the back of a one dollar bill. During the attack he is going to see Frankenstein (a new movie at the time) which was released in 1931. The current back of the one dollar bill was not released until 1935.

Continuity: In the end, when Aaron and his parents are walking at the fun fair, they are holding an ice cream. The brown Italian ice cream of the boy changes from right hand to left hand between shots.

Continuity: When Hancock puts Mary on the hospital bed after she's been shot, the blood on her shirt changes drastically from shot to shot.

Plot hole: During the opening chase scene, Hancock smashes a highway sign, causing multiple police car wrecks. But rather than simply crashing, at least two of the cars vault into the air, flipping end over end, as if catapulted by something, but nothing is exploding nor forming ramps to launch them. They just turn over as if tossed by an invisible force.