Toxic organic pollutants with low biodegradability are observed and detected in industrial wastewater with high contents. Phenol is one of the toxic organic compounds, and discharging it into the water can be extremely harmful to the environment and the organism's health. In this contribution, the photodegradation of phenol and minimizing COD concentration in industrial wastewater collected from the pharmaceutical industry utilizing mesoporous TiO2 nanoparticles (NPs) contrasted with commercial TiO2 photocatalysts have been conducted under UVA illumination. The results indicated that 100% phenol removal and 60.4% of the total COD were achieved at pH = 6, 1 g/L of catalyst loading, and 10.5 mg/L phenol content, 2476 mg/L of COD content within 140 min of UVA illumination. The phenol photodegradation and COD removal over the mesoporous TiO2, UV-100, and P-25 obeyed a pseudo-first-order model, and their rate constants (k) were determined about 0.0175, 0.0091 and 0.0127 min−1. The k value of mesoporous TiO2 NPs was enhanced 2 and 1.4 folds greater than that of the photocatalysts of UV-100 and P-25. The photodegradation of phenol using mesoporous TiO2 NPs for being recycled five times without losing was acquired, which indicated the obtained mesoporous TiO2 NPs are very stable for long illumination time. The active species' role during photocatalytic degradation phenol and COD removal over mesoporous TiO2 photocatalyst under illumination are the critical oxidative species of •OH and O2•− radicals. Consequently, the COD reduction and complete phenol removal in real industrial wastewater have been verified.