CdZnTe, Cadmium zinc telluride (CZT) is an interesting room temperature radiation detector. This research paper is reporting a negative capacitance behavior of CZT detectors at bias voltages around 60V. Initially at 0V, the CZT capacitance is positive and decreases with bias voltage increase. At around 60V, the measured capacitance approaches zero, then with small voltage increase, capacitance value reverses sign and starts to increase in the negative direction with increasing bias voltage. This effect is stable at 100 kHz. The behavior of low and other quality detectors can differ, low quality detectors can show negative capacitance at low bias voltages and low frequencies. The initial explanation of this phenomena is due to non-uniform distribution of impurities inside the bulk material.