Numerical investigation of unsteady natural convection flow through a fluid-saturated porous medium in a cubic enclosure which is induced by time-periodic variations in the surface temperature of a vertical wall was considered. The governing equations were written under the assumption of Darcy-law and then solved numerically using finite difference method. The problem is analyzed for different values of amplitude a in the range 0.2 ≤ a ≤ 0.8, the Rayleigh number, Ra=200, Period, τ = 0.01, time,

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... 0 ≤ t ≤ 0.024. It was found that heat transfer increases with increasing the amplitude. The location of the maximum fluid temperature moves with time according to the periodically changing heated wall temperature. Two main cells rotating in opposite direction to each other were observed in the cavity for all values of the parameters considered. The amplitude of Nusselt number increases with the increase in the oscillating amplitude. All the results of the problem were presented in graphical form and discussed.