Iron-oxide nanoparticles were functionalized with epoxy groups and were dispersed into a dicyclo-aliphatic epoxy resin to obtain organic-inorganic hybrid coatings via cationic ring-opening photopolymerization. TEM investigations confirmed that the filler has a size-distribution range between 5 to 20 nm, without the formation of aggregates. The influence of the presence of Fe2O3 on the rate of polymerization was investigated by real time FT-IR spectroscopy. Increasing the iron-oxide nanofiller in the photocurable resin induced an increase in the Tg values. By controlling the phase separation it was possible to obtain transparent iron-oxide nanostructured coatings, characterized by improved hardness