It is shown that intrinsically stiff chain aggregates of a metallosupramolecular coordination polyelectrolyte (MEPE) can form in the cylindrical nanopores of MCM-41 and SBA-15 silica by self-assembly of its constituents (metal ions and organic ligand). The UV/vis spectra of the resulting MEPE-silica composites exhibit the characteristic metal-to-ligand charge transfer band of the MEPE complex in solution. For the MEPE-silica composite in SBA-15 an iron content of 1.2 wt % was found, corresponding to ca. 10 MEPE chains disposed side by side in the 8 nm wide pores of the SBA-15 matrix. In the case of MCM-41 (pore width < 3 nm), where only one MEPE chain per pore can be accommodated, an iron content of 0.3 wt % was obtained, corresponding to half-filling of the pores. It was also found that MEPE chains spontaneously enter the pores of SBA-15, when a solution of MEPE is exposed to the silica matrix.