In this study, by using a different variety of TiO₂ catalyst, photocatalytic oxidation of reactive azo dye used in textile industry and an improvement in the biodegradability of the dye by photocatalytic oxidation are investigated. It was found that the addition of TiO₂ in the photooxidation of dye increased color removal by 30.84 %, the addition of H₂O₂ in the presence of TiO₂ also increased color removal by 33.98 %. The study also examined the effect of TiO₂ obtained from different companies in color removal and it was found that TiO₂ obtained from Merck and Degussa displayed similar effectiveness in color removal. It was further found that, depending on the chemical composition of dye used, the ions, SO₄^2-, Cl^- and NH₄⁺ emerged and that NH₄⁺ was oxidized to NO₂^-. As a result of the 42 h long photocatalytic oxidation, a COD removal of about 85.3 % was achieved. In this study, Langmuir-Hinshelwood kinetic constants were examined and it was found that k=0.971 mg/L min and K=0.176 L/mg. By analyzing respirometric measures of raw and photocatalyzed dyes, it was determined that photocatalyzed dye had higher biodegradability than raw dye. Improvement in biodegradation was proven by the rise of BOD₅/COD ratio from 0.06 to 0.29.