The limited deformation resistance and high brittleness of cement-based materials to some extent restrict their application range. To thoroughly investigate the influence of basalt fibers (BF) in terms of length and content on the mechanical properties of basalt fiber-reinforced cementitious composites (BFRCC), and to expand their application scope, compressive strength tests, flexural strength tests, and scanning electron microscopy (SEM) were conducted. The results indicate that the inclusion of BF provides a modest enhancement in the overall compressive strength of BFRCC. Compared to the Blank (54 MPa), the highest increase in compressive strength, up to 4.89%, was observed with 6 mm length and 1.5 wt% content of BF. BF effectively improves the flexural strength and peak load deflection of BFRCC specimens. Compared to the Blank group, maximum improvements of 17.02% and 52.94% were achieved in the 9–1.2 group. Using the bending toughness coefficient \(\overline{{\sigma_{{\text{b}}} }}\) to quantify the toughening effect of BF on cement-based materials, the maximum \(\overline{{\sigma_{{\text{b}}} }}\) values for BFRCC were observed in the order of 9 mm > 6 mm > 12 mm BF lengths. Relationship curves constructed with BF content indicate that the inclusion of 6 mm BF provides the most stable toughening effect on BFRCC, followed by 9 mm and 12 mm lengths.