Breakwaters are among the most frequently-used coastal protective structures and their stability is vital to avoid turbulence at the ports. The main purpose of the present research is to use the theory of fuzzy random variables and the second-order reliability method (SORM) to study the reliability of a rubble-mound breakwater against the failure due to the armor layer instability. The limit-state function used for the reliability analysis is obtained from van Gent stability equation for two different modes of wave breaking: plunging and surging. The data used in this research are extracted from the western branch of Anzali Port breakwater. First, a fuzzy inference system (FIS) has been created using MATLAB and the results have been provided including surfaces between random variables with respect to limit-state function and cumulative distribution of each random variable. Afterwards, the formulation of limit-state function, sensitivity study, and second-order reliability analysis have been implemented using Rt software and the final results are presented including variable inference, correlation coefficients, probability of failure, reliability index, sensitivity and importance measures and sensitivity of probability of failure and reliability index with respect to changes in moments of each random variable.