© 2017 American Society of Civil Engineers.This paper investigates the effect of uncertainty in the hydraulic conductivity and van Genuchten fitting parameters used forunsaturated flow modeling of transient seepage through embankment dams. Random variables of the parameters are generated using a numbergeneration algorithm and are then coupled with the finite element software SEEP/W. Stochastic analyses are conducted via Monte Carlosimulation. The statistical and probabilistic properties of the seepage rate passing through different embankment dams and transient boundaryconditions are assessed and the degree of uncertainty associated with the seepage is evaluated. It is found that the probabilistic properties ofthe seepage strongly depend upon the boundary conditions of the dam. The seepage through embankment dams is found to follow thegeneralized extreme value or three-parameter lognormal distributions.