Having more than 2000 km tidal coastline, it's expected that Iran could exploit marine renewable energies. Furthermore, marginal countries around these seas are going to develop their energy resources and marine current energy can be a reliable choice. So, the results of a three dimensional numerical model for the study of circulation in the Persian Gulf and the Gulf of Oman, have been used to assess the power density of ocean currents in these prominent water basins. The calculations are performed regarding converter's dimension and accessibility of the generated power. The results show that the current energy, in the upper 50 m layer increases in two periods of the year, late winter to early spring and late summer to early autumn. It can be asserted that the current energy in the study area increases during monsoon periods. According to the model results, the marine current energy in the Persian Gulf and the Gulf of Oman is rather substantial; but it should wait for harnessing as more efficient power conversion systems are available.