Polymer matrix composites are popular for construction, aerospace and automotive industries due to offer manufacturing and handling ease. In the polymer matrix composites, polymer concretes have high strength. In this study, physical and mechanical properties of lightweight polymer concrete would be investigated by using pumice lightweight aggregate. In the production of polymer concrete, pumice aggregate in maximum size of 12 mm was used as lightweight aggregate. Pumice aggregate has indented and half-open porous surface texture, so it supplies a good bonding between the aggregate and binder paste. As binder material, epoxy resin based polymer was used with its hardener material. The binder/aggregate ratio was in ratio of 30% by weight. In addition, steel fibers were added to lightweight polymer concrete mixtures in ratio of 0%, 0.5% and 1%. After lightweight polymer concrete mixture was prepared, it was poured in the molds in size of 10x10x10 cm then, they were cured at 60 degrees C for two hours. On the hardened lightweight polymer concrete, compressive strength tests were determined. Moreover, ultrasonic pulse velocity, water absorption by weight, specific porosity and density experiments were carried out. The relation between physical and mechanical properties showed that polymer lightweight concretes become more durable depending on using ratio of steel fibers.