In this study, response surface methodology, based on face-centered composite design was used to investigate the effect of operational parameters on the decolorization of methylene blue (MB) using an immobilized film of TiO₂ onto glass plate under a 55-W household fluorescent lamp irradiation. Three operating variables, namely TiO₂ loading (0.65–3.9 mg/cm²), pH (2–10), and irradiation time (15–90 min) with a total of 20 individual experiments conducted to optimize the combination effects of the variable. The significance of the model and regression coefficients was tested by the analysis of variance. Analysis of the data obtained showed there was a strong significant influence of the operational factors and their interactions on MB color removal (p < 0.0001) of the photocatalytic decolorization process. The results predicted by the models were found to be in good agreement with those obtained by performing experiment (R² = 0.9706 and Adj-R²= 0.9442). For MB color removal, the photocatalytic decolorization process was significantly influenced by the pH and irradiation time, whereas the TiO₂ loading shows less effect. The optimum TiO₂ loading, pH, and irradiation time were found to be 3.06 mg/cm² (thickness = 42.43 ± 1.15 μm), 8.25 and 89.76 min, respectively. Under optimum conditions, high photocatalytic efficiency for MB color removal, 98.01% was observed. The kinetics of MB decolorization at optimum conditions was well fitted to the pesudo-first-order kinetic model.