This is the first paper to report a series of bismuth oxyfluoride/bismuth oxyiodide (BiOF/BiOI) nanocomposites with different F/I molar ratios, pH values, and reaction temperatures that were synthesized through a template-free and controlled hydrothermal method. These nanocomposites were characterized through scanning electron microscope energy dispersive microscopy (SEM-EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and diffuse reflectance spectroscopy (DRS). Under visible-light irradiation, the BiOF/BiOI composites exhibited excellent photocatalytic activities in the degradation of crystal violet (CV) and 2-hydroxybenzoic acid (HBA). The order of rate constants was BiOF/BiOI > BiOI ≫ BiOF. The photocatalytic activity of BiOF/BiOI composites reached a maximum rate constant of 0.2305 h, 1.2 times higher than that of BiOI and 100 times higher than that of BiOF. Thus, the derived BiOF/BiOI is crucial for photocatalytic activity enhancement. After the removal of CV in the third cycle, no apparent deficits in photocatalytic activity were observed, and the observed deficit was 8.2% during the fifth run. Overall, the catalytic activity and stability observed for the proposed composites were determined to be adequate under visible-light irradiation. For various scavengers, the noted quenching effects demonstrated that reactive O has a notable role in the degradation of the applied CV.