Continuity: Anna Valerious stabs one of the vampire women in the chest towards the end of the film outside Dracula's castle and wen hear and see her pull the silver stake out. But in the next shot, we see the vampire with the stake in her chest again.

Errors in geography: When van Helsing, Carl and Frankenstein's Monster pass under a bridge and one of the brides shows up and mentions that they are in Budapest, but the National Theater is visible, revealing that it was shot in Prague.

Continuity: When van Helsing, Carl and Frankenstein's Monster pass under a bridge, just before one of the brides shows up and mentions that they are in Budapest, Frankenstein's Monster's right hand is a wooden stake. For the rest of the film, he clearly has a hand there.

Continuity: When we first come to the All Hallow's Eve celebration, Dracula and Anna are not wearing masks. But in the next shot, both of them are wearing masks which they then remove.

Continuity: When Van Helsing and Anna fall down through the rubble of the windmill they are soaked from the rain but when they wake up Anna's hair is dry and curly.

Continuity: During the horse carriage chase sequence, Van Helsing is tearing through a narrow canyon with steep rock faces on both sides towering above the roof of the carriage. However, when Van Helsing is shown sitting on the coach-box from the side perspective, forest trees can be seen in the background instead of the rock faces.

Continuity: When Dracula is front of the large mirror in the ballroom, none of the dancers' reflections can be seen because they are vampires. Previously, though, when the camera was pulling in on the dancers, we saw their reflections in a mirror on the left-hand side.

Continuity: When Van Helsing puts his hand through the secret doorway to the winterland fortress, it is snowing heavily there. However, when the heroes pass through the doorway 10 seconds later, it's raining and there's a thunderstorm.

Continuity: When Anna bounds off of the roof and hits her head on the tree she has a bruise on her head when she lands. After the fight in her castle she shows no sign of a bruise

Continuity: Van Helsing is bitten by the WolfMan on the left hand side of his chest but towards the end of the film when he is about to turn into a werewolf the mark is on the centre of his chest.

Revealing mistakes: The stake that Van Helsing uses on Dracula wiggles when Dracula jerks it out of his chest.

Revealing mistakes: The glass of blood one of the Brides drinks leaves a pulpy residue on the glass--a trait of tomato juice.

Revealing mistakes: The horses fail to react in any manner whatsoever to Van Helsing jumping and crashing into them (caused by real horses and a CGI-produced actor).

Continuity: Dracula throws the telescoping silver stake away after Van Helsing uses it on him. Later, he has it (he gives it to Carl just in case), but he did not have a chance to pick it up, nor did Carl pack more than one.

Errors in geography: Van Helsing uses a carriage to travel from Transylvania to Budapest. After he crosses the Carpathian mountains, the map informs us that he is nearing Budapest. However, the scenery through which he is driving is a mountainous region - quite unlike any terrain near Budapest.

Incorrectly regarded as goofs: At one point, Carl and Van Helsing cremate the body of a human ally. Even though the Catholic church (which Carl and Van Helsing serve directly) prohibited cremation until Vatican II in 1963, it did permit it for special reasons (e.g. to combat the spread of plague).

Revealing mistakes: The undertaker describes Carl as five foot seven, not the metric equivalent

Errors made by characters (possibly deliberate errors by the filmmakers): When Carl is equipping Van Helsing for dealing with Dracula, he grabs a cross from a rack of crosses and says "You'll need a crucifix..." A cross is not a crucifix unless it has a figure of Jesus is on it, and in this case, the rack contained only crosses.

Crew or equipment visible: In the scene where Igor is thrown on top of a rock by Van Helsing and interrogated: Igor is lifted up off the rock you can briefly see several sheets of white paper either stapled or paper clipped together on the rock. It is probably a script left there by the actors.

Continuity: When Anna first encounters Dracula's bride, Aleera is wearing both earrings. When Aleera talks to Anna, her right earring is missing. But when Anna sees Aleera again, with the dead man, both earrings are on.

Source: IMDB