Fatigue life of fiber reinforced concrete (FRC) is theoretically analyzed with a fracture mechanics based model. The model accounts for the effect of cycle-dependent crack bridging properties in FRCs and predicts the number of cycles to failure defined by final fracture subsequent to stable fatigue crack growth in Mode I. The resulting theoretical S–N diagram was compared with experimental data reported in literature. The general agreement supports the validity of the current model, and reveals that cycle-dependent degradation of crack bridging controls fatigue life of FRCs. S–N diagrams are essential for material evaluation and structural design, and the model establishes the link between material structure and S–N diagram in an explicit manner, while the conventional stress-life approach realizes the link in an empirical manner.