Due to the wide existence of shear stress in the mine backfill materials, the shear behavior of polypropylene fiber reinforced cemented paste backfill (FR-CPB) plays a crucial role in the safe design of exposed backfill mass in underground mines. Moreover, warmer curing temperature induced by geothermal gradient influences the evolution of geomechanical behavior of FR-CPB with curing time. Therefore, this study was conducted to investigate the curing temperature (20 °C, 35 °C, and 45 °C) and time (7, 28, and 90 days) dependence of the shear behavior of FR-CPB. The results showed that warmer curing temperature enhances the strain-hardening and softening behavior at early ages, while the pre-peak strain hardening behavior of FR-CPB becomes unnoticeable at advanced ages. Moreover, 90-day shear stiffness, cohesion, dilation angle, and brittleness index of FR-CPB with a fiber length of 13 mm and a fiber content of 0.5 wt% respectively increase by approximately 68%, 62%, 63%, and 65% as curing temperature increases from 20 °C to 45 °C. However, the angle of internal friction is insensitive to the changes in curing temperature. Additionally, predictive models were proposed for the evaluation of the shear properties of FR-CPB. The findings from this study can contribute to the successful application of polypropylene fiber reinforcement technique and sustainable reuse of waste tailings in the underground mine backfill operation.