There is provided a control device, an imaging system, and a 3D model data generation method capable of appropriately extracting a subject from a moving image. The control device includes a control unit that performs control to synchronize an imaging timing at which an imaging device performs imaging with a display timing at which a display device located in an imaging range of the imaging device displays a first moving image, and an image processing unit that performs foreground/background difference processing on the basis of a second moving image captured by the imaging device at a first timing and a third moving image captured by the imaging device at a second timing different from the first timing. The second moving image and the third moving image both include at least a part of the first moving image whose display timing is synchronized between the second moving image and the third moving image. The present technology can be applied to, for example, an imaging system for capturing a moving image used for generating a 3D model.