An efficient sonophotocatalytic degradation of reactive blue 19 (RB 19) dye was successfully carried out using sulphur-doped TiO₂ (S-TiO₂) nanoparticles. The effect of various treatment processes that is sonolysis, photolysis, catalysis, sonocatalysis, photocatalysis, and sonophotocatalysis were investigated for RB 19 removal. S-TiO₂ were synthesized in 1, 3 and 5 wt % of sulphur by sol-gel process and characterized by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX), UV-Visible diffuse reflectance spectra (DRS). The results confirm anatase phase of TiO₂, porous agglomerate structure, and a red shift in the absorbance spectra of S-TiO₂. The dye degradation was studied by using UV-Vis spectrophotometer at λ_max = 594 nm. The reaction parameters such as pH, catalyst dosage, initial dye concentration, ultrasonic power and effect of sulphur doping in different weight percent were studied to find out the optimum degradation conditions. Optimum conditions were found as:S-TiO₂ = 5 wt %, catalyst (S-TiO₂ 5 wt %) = 50 mg, RB 19 solution concentration = 20 mg L^-1, pH =3, ultrasound power = 100 and operating temperature = 25 ^oC.The response of 5 wt % S-TiO₂ was found better than 1 and 3 wt % S-TiO₂ and other forms TiO₂. The sonophotocatalysis process was superior to other methods. During this process the ultrasound cavitation and photocatalysis water splitting takes place which leads to the generation of ^●OH. As reveled by the GC/MS results the reactive Blue 19 (20 mg L^-1) was degraded to 90 % within 120 min. The S-TiO₂ sonophotocatalysis system was studied for the first time for dye degradation and was found practicable, efficient and cost effective for the degradation of complex and resistant dyes such as RB19.