This paper investigated the calcium leaching from plain and fly ash/limestone blended cement mortars under an electric field. The Ca2+ leaching degree and reduced CaO content were measured to assess the extent of calcium leaching, and the compressive strength loss was used as an indicator to evaluate the degradation of the mortars due to leaching. Additionally, the changes in mineralogical composition, micrograph, Ca/Si ratio of C-S-H gel, and pore structure of leached samples were analyzed through X-ray diffraction (XRD), scanning electron microscopy (SEM/EDS), and mercury intrusion porosimetry (MIP). The findings indicated a notable acceleration in the leaching of Ca2+ due to the application of an electric field. Consequently, the calcium leaching degree of mortars continuously increased with time. The accelerated calcium leaching resulted in the loose microstructure and increased porosity mainly for the cathode part as well as the reduction in compressive strength of mortars. The addition of fly ash was beneficial in reducing the calcium leaching and strength loss of mortars after 90 days of exposure to the electric field, contrary to the effects observed with the incorporation of limestone powders. Attention should be paid to the durability issues of cement-based materials induced by the electric field.