In this study, nanodiamond (ND)–titanium dioxide (TiO2) composite nanostructures were designed as inorganic UVblocking materials, and a Couette–Taylor (CT) reactor–based synthesis strategy scalable to a continuous process was proposed. Surface charge modification of TiO2 using polyethylenimine (PEI) enabled electrostatic bridging with negatively charged ND, resulting in the stable formation of ND–TiO2 composites under optimized conditions. Systematic analysis of ND loading revealed that, at an equivalent TiO2 content, the ND–TiO2 composites exhibited enhanced UV absorption compared to bare TiO2, with the most pronounced optical synergy observed at a TiO2:ND molar ratio of 1:4. Furthermore, continuous synthesis under Taylor vortex flow in the CT reactor enabled the formation of uniform composite assemblies with reproducible optical responses even at short residence times. This work demonstrates an integrated material–process design strategy for the scalable production of ND– TiO2 composite nanostructures for UV attenuation applications.