Mn/p-Si Schottky barrier diode (SBD) electrical parameters and interface state density have been investigated with current-voltage (I-V) characteristics and Cheung's functions employing hydrostatic pressure. The interface state density of the diodes has an exponential growth with bias from the midgap towards the top of the valance band. We have seen that the Schottky barrier height (SBH) for Mn/p-Si SBD has a pressure coefficient of 1.61 meV/kbar (16.1 meV/GPa). We have reported that the p-type barrier height exhibited a weak pressure dependence, accepting that the Fermi level at the interface do not shift as a function of the pressure.