© 2016 American Society of Civil Engineers.Sensitivity analysis is conducted to investigate the effects of uncertainty in hydraulic conductivity and van Genuchten parameters on transient seepage. To this end, a random number generator is used to generate random values from probability distributions of each parameter. The generator is coupled with finite-element software that handles seepage analysis in porous media. The Monte Carlo simulation approach is adopted for stochastic seepage analyses. The suggested method is applied on a homogeneous dam made of clayey sand. Uncertainties in each parameter are considered individually in different cases for rapid drawdown and rapid fill conditions. The results show that a variation of hydraulic conductivity has significant effects on transient seepage, and it is suggested that it should be treated as a random variable. However, the effects of the van Genuchten parameters on seepage are found to be insignificant, such that they can be treated as deterministic variables.