Mining methods use cemented tailings backfill (CTB) for filling mined-out voids and make operations safer since employees are working under it. Hence, the durability behavior of CTB is of great importance in applications, for example, in the assessment of slope stability when extracting ore left in neighboring stopes. Addition of cement content would increase the strength of CTB but creates extra costs to mines. To cut cement-related costs as well as improve durability, different types of fibers are added to CTB samples. This paper aims to analyze flexural behavior of fiber reinforced CTB samples under three-point bending loading. To do so, a comprehensive laboratory work was undertaken to explore the effect of fiber reinforcement on bending resistance of CTB samples, based on orthogonal experimental design. The effect of fiber type (FT), fiber content (FC), solid content (SC) and cement-to-tailings ratio (c/t) on bending characteristics was investigated. Results indicate that the addition of fiber enhances the bending strength of fiber reinforced CTB samples and the bearing capacity after the peak in the load-deflection curve. Fibers help correct the faintness of CTB samples by mobilizing tensile strength along the failure planes. The crack resistance of fiber is reflected in the crack propagation stage. Secondly, the order of the sensitivity of four factors on bending strength of fiber reinforced CTB samples is as follows: c/t > SC > FT > FC. Lastly, the main findings of this study can provide a major reference for CTB's last design in underground mining.