The incorporation of Alfa fibers into a cementitious matrix leads to an improvement in the mechanical properties of the composite, particularly its flexural strength. However, degradation of the Alfa fibers over time has been noted due to the high alkalinity of the cementitious environment. In our previous work, five treatments were selected: Chemical (alkaline and hydrothermal), biological (enzymatic), physical (ultrasonic), and mineral coating (sulfoaluminate cement). Although the most effective treatments were alkaline and hydrothermal, all the treatments provided fiber protection, improving the composite properties after 90 days. The aim of this study is to evaluate the performance and durability of mortars reinforced with treated Alfa fibers. Several tests were carried out to measure their behavior under environmental conditions. Mortars containing treated fibers showed that the mechanical performance of fiber-reinforced composites was maintained for up to 70 wetting/drying cycles. In conclusion, mortars with 1% vol. of Alfa fibers, 10 mm in length, treated with alkaline and hydrothermal methods, may be suitable for the development of materials for construction.