In this study, sensitivity of earthquake dynamic response of embedded structures to properties of the structure, surrounding soil, and friction coefficient at soil-structure interface are investigated numerically using Monte Carlo method. The mean soil models represent two of the existing nuclear power plant sites in the United States. For soil, initial shear modulus, shear strength, and a parameter defining the nature of inelastic backbone curve, and for structure, elastic modulus and equivalent viscous damping ratio are considered as the uncertain parameters. It is found that the mean stochastic responses (roof acceleration, roof drift, base velocity) are more sensitive to variability in ground motion than uncertainty in material properties. Mean stochastic response is found to be within 10% of the deterministic response (obtained using mean model parameters) for more than 90% of cases considered. Within the scope of this study, variation in peak velocity at the base of the embedded structure is insensitive to randomness in material properties. Uncertainties in friction coefficient at soil-structure interface is less significant than uncertainties in soil and structure material properties. Roof acceleration in the embedded structure is most sensitive to randomness in soil properties particularly for site subjected to larger shear strain in soil (~ 0.5%).