Unfired four-hole hollow brick (UFHB) is a type of environmental-friendly brick with low energy consumption. However, the using of ordinary Portland cement (OPC) in UFHB is costly and indirectly affects the environment. This paper focuses on an exploratory study on the use of blended fly ash (FA)-OPC in the production of the UFHB and proposes the application of FA-OPC mixtures as a timely solution for the reduction of OPC in UFHB. The 80×80×180 mm UFHB samples were produced using different proportions of FA and OPC under a constant coupled-static forming pressure. The report exhibited experimental characterizations on physical and mechanical properties of both starting materials and UFHB products. In addition, a scanning electron microscope (SEM) analysis was used to evaluate the microstructure of the final UFHB. Test results show that the inclusion of FA in the UFHB mixtures provided positive effects on brick properties. As a result, 10% FA was found as an optimal content, which resulted in the highest brick’s strength, the lowest water absorption rate, and a denser microstructure. Furthermore, properties of all of the UFHB samples produced for this study satisfied the requirements of the National Vietnamese standard for non-bearing building brick.