Continuity mistake: In the scene when Conan's mother is killed, we see her using both hands to hold her sword toward Thulsa Doom and his men. The camera cuts to young Conan and he is holding her right hand. When the camera cuts back to her, she is holding the sword with both hands again.
Continuity mistake: Another one from the beginning of the film when Conan's mother is killed. Conan's mother is holding a sword, protecting her son. Thulsa Doom climbs down from his horse, takes off his helmet, and casts some kind of spell on her with his eyes. She lowers her sword and Doom slowly turns away, then spins quickly and cuts off her head. When the camera cuts to a longer shot, we see that Doom is about 15 feet away from her, much too far to reach her with a 3 foot sword.
Continuity mistake: Just after his meeting with Moko (the "wizard"), Conan gets some flowers to take with him to the Mountain of Power. The color of the flowers change from scene to scene (they start out purple, but when Conan arrives at the base of the Mountain of Power, they're white/yellow) Note: this isn't a matter of Conan needing to get more flowers because of the great distance between the mounds (where the wizard lives) and the mountain of power. The scene transition from the Mounds to the Mountain of Power suggest a day's travel, and similarly Doom takes about a day to get to the Mounds from the Mountain of Power after Conan steals the princess. Flowers don't wilt and need replacing in a day's time.
Continuity mistake: After Conan comes down from Valeria's funeral pyre, you see him throw down the torch he used to light it and everyone is in the dark. The film then cuts to a long distance shot from behind the rocks to show Valeria's pyre exploding again and you can see the torch in Conan's hand.
Continuity mistake: When Conan is captured and Thulsa scolds him for killing his snake, Conan's cloth is in rags by his elbow. Then in a close-up the cloth is not that torn apart and it's over his shoulder. Then a baddie rips it and back to a wide angle with the cloth in rags by Conan's elbow again. The close-up angle should've come first of all.