The term photocatalysis is used to describe a photon-driven catalytic process. Titanium dioxide is a well-known photocatalyst in such fields as self-cleaning material and anti-microbial effects. Besides these photocatalytic applications, TiO2 is a widely-used high index material for optical thin films. In the present investigation, the photocatalytic activity of transparent TiO2 thin films was optimized to achieve multifunctional high precision optical coatings. The films have been deposited by ion assisted deposition (IAD), applying a Leybold APS plasma source as well as a Denton CC-105 ion source. The cause-and-effect chain between the use of different parameters in the IAD process and optical properties of the TiO2 layers as well as their photocatalytic activities are described. As test reaction for the determination of the photocatalytic properties, the degradation of methylene blue (MB) was chosen. The used setup based on a high precision two-path laser measurement system was developed by the LZH in order to determine the kinetic performance of TiO2 catalysts under well-defined UV illumination conditions. Photonic efficiencies of the TiO2 thin films were calculated from the obtained data. Additionally, crystal structure analysis has been investigated for the identification of anatase and rutile modifications. The comparison of the results shows that ion assisted deposition is an appropriate technology for the preparation of photocatalytic active thin films for optical applications.