Ultra-high frequency (UHF) radio frequency identification (RFID) system suffers from large leakage of the carrier due to insufficient TX-to-RX isolation. A narrowband leaking carrier canceller (LCC) for UHF RFID is proposed to enhance the isolation. Hardware realization is carried out based on simulation model in ADS (advanced design system). Measurement results indicate that the TX-to-RX isolation is improved from 20 dB to above 40 dB within UHF RFID frequency band of 920-925 MHz. Upper limit of increase in isolation versus amplitude and phase distortion are also presented and discussed.