USA Today boxes visible in background of scenes on Miami Beach early in the film, just after Tony leaves the government camp. USA Today did not begin service in Florida until the fall of 1982, while the scene takes place shortly after the April 1980 Mariel Harbor boat lift.
After Tony shoots Hector after the chainsaw shootout scene, we hear police sirens but they never become any louder, thus indicating it's just an added sound effect and there aren't any real police cars on the way.
In the double cross scene when Hector throws the chainsaw out the window we see blood all over it, but in the next shot when Hector jumps out the window and lands on the floor with the chainsaw and when we see him on the floor injured the chainsaw is spotless and all the blood is gone.
After Tony and Manny finish talking to Omar for the first time, and about to quit the cafe, a man in a tan shirt and white pants is using the telephone in a booth in front of the cafe. As they walk away the cafe owner asks where they're going, and Tony throws the apron at him and retires. The man is not in the telephone booth in the close up shots of the cafe owner. There is a cut back to a widescreen shot as they continue to walk away and the same man is back in the telephone booth.
When Tony gets shot and falls into the pool during the final shoot-out, another man has been already fallen down to the pool and the blood was everywhere. However, when Tony falls down, the pool was all clean.
The eponymous scar moves and often seems to disappear altogether throughout the film. As an example, when Tony and Manny are driving back from The Babylon, there are a number of head shots where Tony looks to his right to speak to Manny, when his left cheek can clearly be seen with no trace of a scar. Sometimes it is seen below the outer corner of Tony's eye, sometimes it is below the center of his eye.
When Chi Chi first enters the motel room, Hector throws his briefcase at him. The goon crouched behind the bed starts firing the machine gun and several holes strike the wall near the light switch. In the next shot, the bullet hole closest to the switch is gone.
When Tony is in the jacuzzi and Elvira leaves the room calling Tony an asshole, the door is closed behind her. But when Manny gets up and announces he's going on a date and walks to the door, it is wide open.
When speaking with Sosa in Columbia, Tony is seen with a red undershirt and a jacket. Immediately after saying "you want to go on with me? Say it. You don't? Then you make a move". Tony is shown with an open suit jacket, briefly revealing buttons that would have been unseen on his red undershirt. The very next scene shows his outer jack closed again.
When Manny gets Tony, after basketball, both walk towards the gate, meanwhile a bearded character with a spotted brown shirt is walking behind them in and out of the camera for no apparent reason, when Manny and Tony reach the gate to check the incoming Rebenga, that same bearded brown-shirted man enters through the gate from outside, this time wearing a hat and with a limp leg.
When Tony and the guys are following the white car outside the United Nations building to blow it up remotely, there are two beer cans and two food containers on the dashboard of their car. In the exterior shots of Tony and the guys in the car, the beer can closest to Tony is partially crumbled. But in the interior shots of Tony's point of view, the crumbled beer can is perfectly straight and not crumbed. The beer can is crumbled in the exterior shots and undamaged in the interior shots.
When Tony and Angel go up to Hector's apartment to make an attempted purchase of drugs, the sun is shining from the west side of the north-south street (an afternoon shot). In the next scene when a girl standing in the street is flirting with Manny in his get-away convertible, the sun is shining from the east (a morning shot). In the next scene when Tony chases Hector down to the street to finish Hector off, the sun is again on the west side of the street (a late afternoon shot).
When Tony, Manny and Elvira are in the restaurant, Elvira changes position between shots. In one shot she's holding a cigarette in her left hand with her arm above the table. In the next shot her left arm is down and her right is above the table, holding her glass.
Immediately following the shoot-out in the nightclub, Tony and other customers run out, jump into cars from the valet parking lot and drive off. An impossibility - valet parking keys are always kept in a coded cabinet system that requires patrons to identify themselves; keys are never left in cars.
When Tony is with Omar and Sosa in Bolivia, Tony gripes about losing one out of nine loads due to drug interdiction in many forms, including what he calls "EC-2"s...he is probably referring to the Navy's E2-C "Hawkeye", a dual-turboprop radar interception aircraft. In addition, those "Hawkeye" flights were authorized to begin in March of 1982, months after the Bolivia meeting.
During the shower/chainsaw scene, Tony fights with one of Hector's men, takes his pistol away, and shoots him. The pistol is supposed to be a semi-automatic 9mm Beretta 92, but when Tony fires a single shot, the hammer stays down, the slide never recoils, and no casing is ever ejected. The gun is clearly a single-shot prop gun.
The goof items below may give away important plot points.
In the final scene, after Tony gets shot and loses his gun, and he starts yelling, the enemy shooter in the top left-hand corner is still shooting (you can see the shells flying out), but there is no flash or sound.
Before Tony shoots Mel, Mel has a snub nose revolver in a holster on his right hip. Mel never puts his hands near his gun. After Tony shoots him the first time the revolver is now gone and Mel has an empty holster. When he is shot the second time and falls to the floor there is still no gun in the holster and the gun is nowhere to be seen.
Octavio's hat falls off when he first gets shot by the two nightclub hit men. A couple of seconds later, after several cuts, he's shot again, and his hat is not only back on his head but this time it doesn't come off.
In the Hector scene, after Manny is shot by the goon with the revolver, the goon picks up dead Marta's machine gun. The next shot is an over-head view showing the goon still holding the revolver and the machine gun is on the bed.
When Tony is shot at the end scene he falls forward into the pool - the railing is pushed outwards. But when the camera looks back up at Tony's killer, it's pointed inwards towards his office. When the killer walks down the stairs, its pointed outwards again.
In the finale, one of Tony's guards, the guy in the tan suit, is shot to death by Sosa's men and he falls face first onto the floor a couple feet from the stairwell. In shots soon after his body has changed positions and he is now lying on his back on the bottom of the stairs.
When Tony is returning to his mansion at the end of the movie, an enemy soldier is seen following the car near the gate. The enemy soldier calls to his friends to jump over the wall near the gate. But, if they are jumping over the wall, that means that more than likely they started from within the mansion grounds.
When Tony's bodyguards are trying to convince him to run, Sosa's agents can be seen in the cameras running onto the grounds. A few minutes later the guards are getting killed by the agents and the same footage is playing on Tony's cameras.