Continuity mistake: Gator's brown Ford sedan alternately does and doesn't have rear bumper guards during the first moonshine chase. (00:40:10)
Visible crew/equipment: Denise arrives at her flat and finds the OAS Member there, with his back to the camera. To his right in the mirror the right half of director Fred Zinnemann's body and forearm is visible for a split second. (00:20:40)
Visible crew/equipment: The morning after the bar shooting, when Charlie and Johnny Boy are in the apartment, we can see the outlines of the hidden mic wires at the front of both of their undershirts, as well as the bulge of the mic transmitter at the back of Johnny's waist. (00:50:35)
Continuity mistake: In the scene where Serpico is in his apartment speaking to his girlfriend explaining how hard it's been to be an honest cop, he is drinking what appears to be a full glass of white wine. In the following shot of the both of them, Serpico sets up two unused glasses, opens a bottle of wine and pours it into the two glasses. His original full glass of wine is nowhere to be seen.
Continuity mistake: Rizzo breaks up the rumble at the pizza joint; in the wide shots when he keeps the goons in check, there are several more unperturbed bottles in the shelves behind Manomozza than in close-ups. Some of the bottles that were in the side shelves in fact have inexplicably moved onto the center one. (00:11:25)
Continuity mistake: When Sgt. Howie first goes to the Post Office, he walks through to where Myrtle is painting the hare. He puts down his leather case which then changes position a few times during the next few shots, until the scene ends.
Continuity mistake: As Shaft is stick fighting in the stable, the Emir's attendant makes a comment about his penis (no, seriously, he does!). The man is leaning against the door with his hand positioned 3 different ways in 3 different shots. (00:13:00)