The formation of microcracks is a major concern for the integrity and durability of concrete and other cementitious composites, since such microcracks cannot be easily controlled and detected within the matrix of composite. This work explored the possibility of using surface-sulfonated polystyrene microspheres (SPSM) featuring an average diameter of 0.7 +/- A 0.5 mu m to improve the crack resistance of carbon microfiber-reinforced mortar. The compressive strength and EIS data demonstrated that the incorporation of SPSM at 0.15% by weight of cement led to a denser and more refined microstructure of the cement mortar composite, likely attributable to the active interactions between SPSM and cement hydration products as well as carbon microfibers. The crack resistance of these cement-based composites was evaluated using a non-destructive test under uniaxial compression loading along with a fatigue test under uniaxial compression cyclic loading. The data, in the form of critical stress, specific crack area, and fatigue strain, revealed that even at a small dosage the incorporation of SPSM to carbon microfiber-reinforced mortar retarded the initiation of unrecoverable microcracks and slowed down the propagation of microcracks under uniaxial compression loading, and improved the crack resistance and toughness of the specimens under fatigue loading.