The electrical conductivity of polycrystalline aragonite (CaCO3) was investigated using a multianvil press in the pressure range 3–6 GPa. The electrical conductivity of the samples was measured using a complex impedance analyzer in the frequency range 0.05–10–6 Hz. A decrease in the electrical conductivity with increasing pressure was observed. The calculated activation enthalpy in the temperature range 800–1000 K increased with increasing pressure. The effect of pressure and temperature were included in the Arrhenius equation, and the fitted data gave an activation energy and volume of 0.40 eV (38.6 kJ/mol) and 9.28 cm3/mole, respectively. The positive activation volume observed in this study suggests that ionic conduction is the dominant mechanism for the electrical conductivity over the pressure and temperature range investigated. The electrical conductivity of aragonite is much higher than that of olivine, which is a major mineral in the upper mantle. Therefore, the subducted slab, which contains a significant amount of calcium carbonate, has a higher electrical conductivity compared with the surrounding mantle.