Abstract: The ordinary cemented tailings backfill (CTB) is a cement-based composite prepared from tailings, cementitious materials, and water. In this study, a series of laboratory tests, including uniaxial compression, digital image correlation measurement, and scanning electron microscope characteristics of fiber-reinforced CTB (FRCTB), was conducted to obtain the uniaxial compressive strength (UCS), failure evolution, and microstructural characteristics of FRCTB specimens. The results show that adding fibers could increase the UCS values of the CTB by 6.90% to 32.76%. The UCS value of the FRCTB increased with the increase in the polypropylene (PP) fiber content. Moreover, the reinforcement effect of PP fiber on the CTB was better than that of glass fiber. The addition of fiber could increase the peak strain of the FRCTB by 0.39% to 1.45%. The peak strain of the FRCTB increased with the increase in glass fiber content. The failure pattern of the FRCTB was coupled with tensile and shear failure. The addition of fiber effectively inhibited the propagation of cracks, and the bridging effect of cracks by the fiber effectively improved the mechanical properties of the FRCTB. The findings in this study can provide a basis for the backfilling design and optimization of mine backfilling methods.