Some aspects of the interaction of (NH4)42[Mo 72 VI Mo 60 V O372(H3CCOO)30(H2O)72] · 30H3CCOONH4 · 250H2O (polyoxometalate Mo132) with a water-soluble nonionic polymer (poly(vinyl alcohol) or related poly(vinylpyrrolidone)) were studied in aqueous solutions and in films. A set of methods was used: spectrophotometry, EPR spectroscopy, visual microscopy, X-ray powder diffraction, scanning probe microscopy, and potentiometry. The complex-formation features of the system were revealed. The miscibility of the components and their influence on crystallization phenomena were considered. The effect of UV and X-rays on poly(vinyl alcohol) + polyoxometalate films was studied. Poly(vinyl alcohol) stabilizes the polymer. Mutual radiation and thermal stabilization of the polymer and polyoxometalate was discovered. The utility of ion-sensitive electrodes for Mo132 determination in solution was demonstrated.