The interference characteristics of a PLC system using Wavelet-OFDM were measured when narrowband interference signals were impressed. The results showed that the PHYsical layer (PHY) rate at the all-frequencies band hardly decreased at all at C(Carrier)/I(Interference) of -10 dB or more, but began to decrease rapidly at C/I of -30 dB or less when interference signals were impressed in the frequency band of the PLC signals. In addition, when C/I became -60 dB, the PHY rate at the frequency corresponding to the notch band became about 10 Mbps higher than that at a frequency not corresponding to the notch band. This demonstrates that a Wavelet-OFDM PLC system has an excellent interference characteristic, on that is fully on a par with that of an FFT-OFDM PLC system.