Continuity mistake: At the front door of Sao Feng's, after Elizabeth removes her hat, it cuts to the removal of her decorative vest (totally skipping her jacket), revealing her weapons' holster harness underneath, and she then tosses her vest at Sao Feng's man. Problem is the man doesn't catch her vest, he actually catches her empty weapons' holster harness. But, in the next few shots she's still wearing that holster harness, as she removes her lovely weapons.
Continuity mistake: The cord necklace Will wears, which has several things dangling from it - particularly a distinctive white shell, flips round the opposite way between shots within a scene, several times during the film. For example, before and after the maelstrom, including the ceremony Barbossa performs.
Continuity mistake: The worn areas of Jack's leather hat drastically changes throughout the film. Additionally, the hat has a threaded 'X' on both its right and left side. In numerous close-ups extra thread holes are visible in different areas near each of these Xs; such as in the Locker, when Jack lies on the ground as the Pearl passes by and later, on the little island, before Jack switches places with Will. In other shots those extra holes are gone, such as when Jack sets sail for the Fountain of Youth. The actual sizes of the Xs also change.
Continuity mistake: When Barbossa is talking to Calypso on the Black Pearl, right after he says, "Masters Pintel and Ragetti, take this fishwife to the brig," there is a shot of Pintel and Ragetti leading her down the deck's steps. The Black Pearl is pitching strongly up and down. In the next shot, where Barbossa looks at and flexes his hand, the ship is barely pitching at all.
Continuity mistake: When Barbossa and Elizabeth go to meet Sao Feng, she is asked to get rid of all her weapons. When she places the homemade grenade on the table, it gets placed on the edge of a red cloth where you can see the table at the end of the cloth, yet when she places her final weapon, the red cloth is now almost completely covering the table.
Continuity mistake: When Jack is on the Black Pearl in Davy Jones' Locker, the are scratches on his right hand. But a few minutes later when Barbossa leads the crew to Jack's rescue, the scratches are gone.
Other mistake: Near the end of the movie, an order is given to fire a cannon shot at the masts of the Pearl and the Dutchman as they have become entangled. We then see a mast being destroyed by the shot but when the ships separate, not one of them has a broken mast.
Revealing mistake: At the beginning of the film, when Sao Feng is introduced, a couple of his real nails are visible under the fake long dirty ones glued atop them. It's most noticeable when he scratches his head.
Other mistake: In numerous shots modern bobbypins (the white kind brides wear on their headdress) are clearly visible inside the curls of the men's white wigs. For instance, they can be seen when Norrington is reunited with his sword; later when he dies; when Beckett talks about the immaterial becoming immaterial; finally, when he says, "It's just good business," as the Pearl and Dutchman fire on Endeavor. The type of 'hair pin' seen in the wig curls did not exist in the mid 18th century.