An automatic score dartboard assembly has a base, a dartboard, a support, at least one imaging element and a main control circuit. The dartboard and the support are attached to the base, and the at least one imaging element is mounted on the support to capture a direct viewing image of the dartboard periodically. The images are output to the main control circuit to determine the score of a dart when the dart sticks in the dartboard. The main control circuit is composed of an image processor and a memory device. The image processor uses an image comparison method to determine the score of the dart. Therefore, the present invention uses as few as one imaging element to determine the score and increases accuracy of determining score.