Abstract: In order to improve the interfacial properties of EB cured composites, the carbon fibers were anodized and coated with an epoxy-based coupling agent. The influence of different electrolytes used in anodic oxidation on the carbon fiber properties was studied. The untreated and treated carbon fibers were investigated by SEM and XPS, and the contact angles were analyzed to better understand the surface properties of carbon fibers. The adhesion between carbon fibers and epoxy matrix was evaluated using interlaminar shear strength (ILSS) testing of the EB processed composite samples and compared with adhesion data for the same fiber in a thermally processed epoxy matrix. It is shown that the carbon fibers treated with acidic electrolyte improve ILSS of EB cured composites; on the other hand, the carbon fibers treated with basic electrolyte decrease ILSS of EB crued composites. The interfacial properties of EB cured carbon fiber reinforced epoxy matrix composites are improved after the carbon fibers have been double-treated.