One of the most important characteristics of concrete is flexural and tensile strength, these two strengths are in fact dependent on the compressive strength and the improvement of each of them will also be effective on the other. In the context of increasing the flexural strength and tensile strength of concrete, the role of the fibers is very significant, especially in lightweight concrete with a greater free space in the aggregates or less density of aggregates. This paper examines the effects of industrial steel and recycled rubber tires fibers on the mechanical properties of lightweight concrete containing Pumice. The amount of industrial and recycled steel fibers in this study (0.5-1% -1.5%) by the volume of concrete and with a length to diameter ratio of 50. Also, additives such as super-plasticizers have been used to reduce water consumption and microstructures pozzolanic materials such as silica fume to fill the pores and concrete voids in order to enhance the mechanical properties of lightweight concrete. It should be noted that the purpose of using recycled steel fibers is to reuse and eliminate environmental problems caused by the burial of these wastes. In this study, eight lightweight concrete mix design containing different percentages of steel fibers were made and compressive strength, tensile strength by splitting and failure modulus have been tested. The results of the experiments show the positive effect of industrial and recycled steel fibers on Mechanical properties of light weigh concrete.