A radiation imaging system includes a radiation imaging apparatus including a radiation detection unit in which conversion elements configured to convert radiation into electric charges are arranged and a driving unit configured to drive the radiation detection unit, and a control apparatus configured to control the radiation imaging apparatus. The control apparatus includes: a determination unit configured to determine whether a remaining image sensing enable time acquired by subtracting an elapsed time from initialization of the radiation detection unit from an image sensing enable time for a radiation image in use of the radiation detection unit is not less than a threshold time; a control unit configured to change operating states of the radiation detection unit and the driving unit in accordance with the determination result; and an operation detection unit configured to detect an operation instruction for the control unit.