Provided is a radiation imaging system configured to synchronize radiation irradiation with operation of a radiation imaging apparatus. The radiation imaging system includes: an irradiation unit arranged to irradiate with radiation; a detection unit arranged to detect the radiation; a setting unit configured to set an irradiation time at which irradiation of the radiation is to be started; an irradiation control unit configured to control the irradiation unit so that radiation irradiation is executed at the irradiation time; and a detection control unit configured to control the detection unit so that the detection unit is ready to detect the radiation at the irradiation time.