Hybrid films composed of dendrimer poly(new fuchsin) and nanometer-sized clusters of silicomolybdate polyoxometalate, SiMo12O40 4−, have been prepared in acidic aqueous solutions. The cyclic voltammograms recorded the deposition of the hybrid films from the direct mixing of new fuchsin and SiMo12O40 4− ions from the solutions. These films are stable and electrochemically active, and can be produced on glassy carbon, platinum, gold, and transparent semiconductor tin oxide electrodes. An electrochemical quartz crystal microbalance and cyclic voltammetry were used to study the in situ growth of the poly(new fuchsin) and SiMo12O40 4− hybrid. The poly(new fuchsin)/SiMo12O40 4− hybrid film showed four redox couples. When transferred to various strongly acidic to weakly acidic aqueous solutions, the four redox couples and the formal potentials were observed to be pH-dependent. The poly(new fuchsin)/SiMo12O40 4− hybrid films also showed a monovalent and divalent cation effect for Li+, Na+, K+, Mg2+, Ca2+, Sr2+, and Ba2+.