Systems and methods for passively calibrating and correcting for I/Q mismatch in a quadrature receiver without the necessity of modifying the analog portion of the receiver by adding calibration signals or correction circuitry are presented. The passive I/Q mismatch calibration system proceeds using normally received incoming transmitted data signals to obtain statistical information on which to base I/Q mismatch compensation factors. The I/Q mismatch compensation factors can be used to adjust the magnitude and phase response in the time domain or the frequency domain, the analog or the digital portion of the receiver. Depending on the embodiment, the passive I/Q mismatch calibration system can calibrate frequency dependent gain or magnitude imbalance, frequency independent magnitude imbalance, frequency dependent phase imbalance, and frequency independent phase imbalance or combinations or these.