A new mathematical model for the analysis of fractally fractured reservoirs is proposed. The diffusion equation including the variation of fracture aperture is derived and solved with Green＇s function approach. The aperture variation can be considered with the concepts of aperture probability-density function and waiting-time distribution. The approximate solution obtained from this equation, indicates that more pressure drop takes place because of the additional delay of diffusion. Also, a sensitivity analysis was carried out for various cases. The model developed in this work makes it possible to characterize the pressure transient of fractally fractured reservoirs in a more realistic manner.