A radiation imaging system includes a detection unit configured to detect a dose of radiation irradiation from a radiation source, a first processing unit configured to output a first stop signal when dose information obtained based on first processing for a result of the detection exceeds a threshold, a second processing unit configured to output a second stop signal when dose information obtained based on second processing on a signal having undergone the first processing exceeds a threshold, and a control unit configured to control the radiation source so as to stop the radiation irradiation based on the first stop signal or the second stop signal.
