Abstract: With the increasing enclosure of modern buildings and the widespread use of decorative materials, indoor air quality has become a critical environmental factor affecting human health. TiO₂ (titanium dioxide) photocatalytic technology is regarded as one of the most promising approaches for addressing diverse indoor air purification challenges owing to its environmental compatibility, high efficiency, and stability. However, the wide bandgap (approximately 3.2 eV) of pure TiO₂ restricts its photoactivity to ultraviolet light (<387 nm), and the rapid recombination of photogenerated electron-hole pairs significantly hinders its practical performance. This article reviews recent advances in modified TiO₂ for indoor air purification. Through modification strategies-including metal and non-metal doping, heterojunction construction, and oxygen vacancy introduction-the material's fundamental properties are enhanced across multiple dimensions: the optical response is extended into the visible-light region, charge carrier recombination is suppressed, and the generation efficiency of reactive species is improved, thereby accelerating the transition toward real-world applications. Nevertheless, most modified TiO₂ materials and their composites remain at the laboratory research stage, and a considerable gap persists before commercial deployment.