Continuity mistake: Frost says near the end of the film that the spirits of the twelve will awaken the Blood God. Fair enough, but when the prophecy is first translated, you hear twenty beeps as pictures of people pop up around the circle, implying that there are twenty people standing around it.
Continuity mistake: In the beginning of the movie when Frost leaves the meeting, as he leaves the sound from his shoes is delayed.
Visible crew/equipment: In the shot where Blade and Karen are running across the rooftop from the police firing at them from the hospital/morgue window, you can see the arms of a man holding a paintball gun on the right side of the screen. Paintball guns were used to fire projectiles that mimic the spark and smoke effects of bullet strikes. (00:15:35)
Continuity mistake: In the subway, Blade and Quinn are fighting on the edge of a subway station for at LEAST two straight minutes as a train barrels by. In NYC, it takes a subway car one to two seconds to pass a stationary point when moving at normal speed. Even being generous and saying two seconds per car, what subway train has sixty cars in it? (normal is eight, I believe). (00:55:00)
Continuity mistake: When Blade is kicking butt in the club, he jumps into a shower, stabs the last guy then jumps onto a side ledge and has the sword in his right hand. When the camera cuts to Quinn then back to Blade, he is switching his sword from his left hand to his right. (00:08:45)
Continuity mistake: Right before the sword embeds the marble, it's on the right side of EDTA. When the sword handle opens it's above it. (01:51:30)
Continuity mistake: When Blade chops off Quinn's hand in the hospital, we see it fall down inches from Karen's face, as she is lying on her front on the floor. After the fight is over, Blade finds Karen lying on her back. It is unlikely that, being as incapacitated as she appears, she would have the strength or inclination to turn her whole body over. (00:14:04)
Audio problem: When Frost first enters the conference room with the rest of the members of the house, the older member with the symbol tattooed on his forehead scolds Frost about how he's not a pureblood. In a shot down the table (probably only noticeable in widescreen), you can see the guy on the right side of the screen, but his mouth isn't moving, even though you hear him talking.