Seismic velocity was used to evaluate the pore pressures of one of the Iranian carbonate reservoirs which was first used by the authors in this type of study. Seismic velocity was executed from seismic multi-attributes analysis method, to study interval velocities. Effective pressures were predicted with Terzaghi equation at well locations by using overburden pressures obtained from density cube and well pressure tests (RFT). An initial relationship was obtained from the effective pressure and seismic velocity data fitting. The required calibration coefficients were determined by performing necessary corrections in the wells, therefore the velocity data cube was converted into effective pressure cube. Our investigation results contain, high correlation coefficient and low mean squares error indicate that pore pressures could be perfectly predicted by seismic velocity data in carbonate formations before drilling. In addition it is also possible to estimate the required mud weights. Such Studies will play a significant role in potential risk evaluation.