Continuity mistake: In the car chase scene when Brock is on the motorcycle going through the city, you can see him pass by the same movie theater at least 3 different times in the chase showing they used the same street over and over while filming.
Continuity mistake: When Dan explains to Eddie what Venom is doing to his body, Venom grabs Dan with his left hand. In the next shot, it's his right hand.
Suggested correction: Venom always has Dan in his left hand. You can especially tell by the position of Venom's thumb.
Visible crew/equipment: When Eddie/Venom is sandwiched between two SUV's, the Symbiote takes over and makes them crash. You can see the hood of whatever vehicle the camera is in as it films the crash.
Suggested correction: After the crash of them going into the vehicles either side, you can see there is a third car in the exact spot as the camera car, so they could say it's the view from that car.
Continuity mistake: After Eddie faints in his bathroom the toothpaste around his mouth disappears.
Revealing mistake: When the ambulance featuring the first Venom incarnation crashes it comes to a very sudden stop, like a piece of metal tipped over onto a magnet instead of sliding under its own momentum. Likely because they didn't animate the transition between the CGI of the crash and the stationary position of the set properly.
Other mistake: When Maria dies after infecting Eddie with the symbiote her head's turned to her right. A shot of Eddie then her again, suddenly her head's turned towards Eddie who's on her left on the floor.