This study centers on the application of photocatalytic process using supported bismuth (III) oxyiodide–multi-walled carbon nanotube (BiOI–MWCNT) composites for the elimination of Metronidazole (MNZ) from its solution. The characteristics of BiOI and synthesized BiOI–MWCNTs composites were analyzed via the scanning electronic microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The photocatalytic study was performed to evaluate the effect of UV (8, 15, 30, and 125 W), irradiation time (10–90 min), pH (5-9), initial MNZ concentration (10-100 mg/L) and BiOI–MWCNTs dosage (0.3–1.2 g/L) on MNZ removal at fixed neutral pH of 7. MNZ concentration was examined via the HPLC by measuring at 348 nm. Higher MNZ degradation was achieved using both BiOI–MWCNTs and UV light than using each separately. Maximum MNZ degradation efficiency of 99.95 % was obtained at pH 7, BiOI–MWCNTs dosage of 0.6g/L, MNZ concentration of 10mg/L, and irradiation time of 90min. MNZ removal was increased by increasing irradiation time and decreasing initial MNZ concentration. Pseudo-first-order rate of reaction (K) based on the Langmuir-Hinshelwood (L-H) model and adsorption equilibrium constant of 1.629 mg/L.min and 0.044 L/mg, respectively were obtained. Also, the adsorption kinetic study fitted the pseudo-first-order reaction. The electrical energy consumption per order of magnitude (E) for MNZ degradation was lower for the UV/BiOI–MWCNTs process than the BiOI–MWCNTs- alone and UV- alone processes. The photocatalytic degradation process using BiOI–MWCNTs can be applied efficiently for the removal of MNZ from aqueous solutions.