Prussian Blue (PB) has been electrochemically grown through thin mesoporous silica films of novel generation, exhibiting regular arrays of hexagonally packed mesopores channels (3 nm in diameter) oriented perpendicular to the underlying electrode surface. Due to confinement effects, special care has to be taken to ensure effective permeability of PB precursors through the hard silica template, which was best achieved by pulsed electrodeposition from a high ionic strength medium (2 M KCl). Energy dispersive X-ray spectroscopy associated to electron microscopy was used to evidence the presence of PB in the vertically-aligned mesopores, which was also assessed by their electrocatalytic behavior towards H2O2 reduction.