(Nb0.5Si0.5)xTi1 xO2 nanocomposites (x =0, 0.025, 0.05, and 0.1) were produced by the easy and versatile mechanical milling technique. Structural parameters, optical absorbance, surface area, and photocatalytic per formance towards methylene blue (MB) under ultraviolet–visible (UV–Vis) radiation were investigated. The structural analysis revealed the formation of rutile and brookite phases, confirming the good incorporation of Nb0.5Si0.5 inside the TiO2 lattice. The crystallite size of formed phases was slightly affected by the dopant and its average value is in the range of 5–7 nm. The morphology of composites is composed of spherical-like nano particles with an average particle size range of 10–22 nm, and the highest surface area (19.19 m2/g) was reached for (Nb0.5Si0.5)0.025Ti0.075O2. The FTIR, Raman, and XPS analyses indicated the formation of numerous Ti–O–Ti, Si–O–Ti, and Si–O–Si bonds and emphasized the formation of rutile and brookite phases. The optical band gap obeyed the direct transition mechanism, and its average values were 3.4, 3.82, 3.7, and 3.5 eV for x =0, 0.025, 0.05, and 0.1, respectively. The photodegradation efficiency (η) of TiO2 towards MB was enhanced by Nb0.5Si0.5 doping, catalyst dosage, pH value, and irradiation time. The maximum value of η towards MB was 76.6 % and was attained after UV–Vis irradiation for 140 min in the presence of 1 g of (Nb0.5Si0.5)0.025Ti0.075O2 catalyst per 1 L MB, with the highest rate kinetic constant of 1.02 ×10 2 min 1. The value of η increased up to 94.34 % by adjusting the pH to 10. The optimum catalyst dosage for the MB photodegradation (96.4 %) is 2 g/L. Moreover, the recycling experiments demonstrated adequate reusability for the investigated catalyst. Furthermore, the adsorbed dye on the surface of the catalyst has been investigated and the degraded products were analyzed using the GC-MS technique, with a postulated mechanism of degradation. Therefore, the prepared (Nb0.5Si0.5)xTi1 xO2 nanocomposites are suitable for the degradation of various toxic dyes and may apply to various technologies required for modulated optical band gaps such as UV photodetector.