Sulfated (5wt.%) ZrO₂ and non-sulfated ZrO₂ modified by NH₄VO₃ using incipient wetness impregnation technique to achieve a loading of 5wt.% V₂O₅ were thoroughly characterized by means of X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy, N₂ sorptiometry, particle size analyzer and pyridine-FT-IR that was used to investigate the acidity of the samples. Degradation of direct blue-1 (DB) dye was tested for the effectiveness of the samples. The results revealed that DB degradation was highly improved with V supported on ZrO₂–SO₄ and showed a conversion comprises of 95% after UV irradiation (emitting at 365 nm) for 60 min exceeding that of SO₄ free ZrO₂ sample (68%) obtained at the same period of illumination. This was due to the large surface area (183 m² g^-1), small crystallites size and presence of basic sites namely O₂⁻ and OH⁻ moieties, those take part in the reaction as additional oxidizing agents. The photocatalytic degradation of DB was found to follow first order rate kinetics. More information on the activity, surface texturing, kinetics and TOC removal were well evaluated, compared and discussed for all samples.