Our present study aims to investigate the optimal use of waste tire rubber as a fine aggregate in concrete and their sensitivity to high temperature effect. Five different concrete compositions were prepared: a reference concrete (RC) made with natural fine aggregate (sand) and coarse aggregate (dolomite) and four concrete mixes with replacement rates of 4%, 8%, 12% and 16% of sand by crumb rubber from waste tires. For the effect of elevated temperature: Similar specimens were exposed to a period of 4 hours to temperature of 70°C, to study the effect of high daily temperature, and a period of 2 hours for both temperatures 200° C and 400° C to study the effect of fire. After cooling down to ambient temperature, the compressive strength, flexural strength and the splitting tensile strength were measured and compared with the values that obtained before fire exposure. The inhand study indicates a gradual decrease in compressive, splitting and flexural strengths of concrete for partial substitution of crumb rubber aggregate in concrete. In addition, more decrease in these strength values are resulted after exposing the similar specimens to high temperature. While the inclusion