This paper presents a preamble-based time and frequency synchronization algorithm for an NC-OFDM-based Cognitive Radio (CR) system. While keeping its computational complexity close to the commonly known, autocorrelation-based Schmidl&Cox algorithm, it is robust against narrowband interference (NBI), e.g. from Primary Users (PUs). Essentially, the proposed algorithm does not require to know any parameters of NBI. Simulations results conï¬rm its usefulness even in the case of a real interference.