In this paper, the effect of presence of NarrowBand Interference (NBI) in Orthogonal Frequency Division Multiplexing (OFDM) system is investigated and analyzed. Wireless transmissions over unlicensed bands mostly face the undesirable effect of NBI. There is significant amount of performance degradation in such systems, thus NBI suppression techniques need to be employed. Some of the NBI suppression methods are frequency excision, frequency identification and cancellation, adaptive notch filtering, use of Least Mean Square (LMS) algorithm, wavelet denoising and spread spectrum techniques. All these techniques improve the performance of an OFDM system with NBI to a different degree.