Miniemulsion periphery polymerization (MEPP) has been used for the synthesis of Prussian blue (PB) nanocubes. Pentacyano ferrate functionalized surfactant in combination with a co-surfactant containing 4-(dimethylamino)-pyridine (DMAP) or OH end groups in lieu of ferrate functionality (EPE-DMAP or EPE-OH) were used to prepare a miniemulsion system comprising 20 wt.-% toluene and 0.5 wt.-% total surfactant. On addition of Fe3+ to the miniemulsion, metal coordination polymerization occurred with nanocubes generated when the ratio of EPE-Fe:EPE-DMAP (or EPE-OH) was 60:40 (w/w). The resulting nanocubes are apparently amorphous. Particles with irregular shape have been observed on reacting EPE-Fe and Fe3+ directly in water, thus suggesting that confinement of the polymerization field on the periphery of the miniemulsion droplets is a primary factor in the formation of cubic structures.