TiO2 supported on Ca12Al14O33 (Mayenite) was synthesized and investigated for use as a photocatalytic concrete material. TiO2/Mayenite (TiO2/M) catalysts were prepared with varying TiO2 loading amounts (1-20 wt%). The photocatalytic activity of the catalysts was measured using the ISO standard NO removal test. TiO2/M catalysts exhibited significantly enhanced photocatalytic activities compared to pure TiO2, with the NO removal efficiency increasing as TiO2 loading increased up to 10 wt% and then decreasing with further loading of TiO2. The NO removal rate of the TiO2/M catalyst, which contained 10 wt% TiO2, was 8.72 μmol (equivalent to 350 μmol/m2∙h). X-ray photoelectron spectroscopy (XPS) analysis suggested that oxygen on the TiO2/M catalysts with low TiO2 loading exists in the form of Ti-OH rather than TiO2. This study focuses on the formation of Ti-OH on the catalyst surface, which is promoted by the unique crystal structure of Mayenite that supplies oxygen ions and electrons to the TiO2 layer. The NO removal efficiency of the catalysts was found to be dependent on the interaction between TiO2 and Mayenite. Overall, this study demonstrates the potential of TiO2/Mayenite for use as a highly effective photocatalytic concrete material, with the unique properties of the Mayenite support playing a critical role in enhancing the photocatalytic activity of the catalyst.