Environmental remediation of xenobiotic pollutants is an important issue in industrialized society. Catalyst‐mediated pollutant photodegradation using solar light shows promising results. Titanium dioxide nanoparticles (TiO2 NPs) are a well‐known standard for mineralizing organic water pollutants. Its use as a sludge pointed out the need to support this photocatalyst to ease both its use and recovery. Polymers represent a viable solution because of their versatility, stability, and cheapness. The in situ radical bulk polymerization approach to the development of TiO2‐based thermoplastic nanocomposites for xenobiotic photodegradation enhances the photocatalytic performance of the semiconductor nanoparticles. The versatility and efficiency of these systems pave the way for their industrial applications as photocatalytic coatings for large‐scale surfaces. To shed light on the influences of the chemical nature of the polymer matrix on the photocatalytic efficiency of the nanosystems, polyvinyl acetate, polymethyl methacrylate, and polystyrene are investigated as supports for TiO2 NPs. The obtained TiO2‐containing nanocomposites are characterized by thermal analyses, UV‐vis, Raman, and X‐ray photoelectron spectroscopies, dynamic light scattering, and contact angle measurements. The photocatalytic activity of the nanosystems in the form of thin films is investigated against pollutants in water solutions, and shows clear differences in the photodegradation efficiency among the nanocomposites having different chemical natures of polymers.