This paper presents Investigation of Transient Fault Effects in an asynchronous NoC router. The experiment is based on simulation-based fault injection method to assess the fault-tolerant behavior of the asynchronous router. The effort has been accomplished by employing fault injector signal (FIS) in 136 targets. 13600 transient and permanent faults have been injected into the CSP-Verilog model of NoC router. Different fault models such as glitch, cross-talk, SEU, and SET have been applied in this effort to evaluate asynchronous NoC Router. The experimental results have been considered in different aspects to estimate the NoC router’s robustness. Although asynchronous designs seem inherently fault-tolerant due to applying handshaking signals, up to 56% of the injected faults result in failure, and about 43% of injected faults are overwritten before turning into errors. Less than 1% of injected faults treat as latent error. Moreover, the failure rate of token generation consumption is higher than token consumption effects.