This paper presents the results of the fundamental loading tests with brick elements strengthened by the epoxy resin injection method. Three types of loading tests were performed to evaluate the effects of epoxy resin injection on compressive, shear, and flexural characteristics. The variables considered in this experiment were the strength of the mortar and the applied axial force. To verify the effects of this strengthening method, seismic loading tests were performed on three brick walls. From the test results, an increase in the strength of the element was observed in each test. However, the strength of the mortar did not affect the shear and flexural strength of the brick elements. We proposed equations to estimate the strength of the elements strengthened by the epoxy resin injection method. Improvements to the seismic performance of the brick wall strengthened with epoxy resin were explicitly confirmed.