Nanostructured inverse hexagonal polyoxometalate composite films were cast directly from solution using poly(butadiene-block-2-(dimethylamino)ethyl methacrylate) (PB-b-PDMAEMA) diblock copolymers as structure directing agents for phosphomolybdic acid (H-3[PMo12O40], H3PMo). H3PMo units are selectively incorporated into the PDMAEMA domains due to electrostatic interactions between protonated PDMAEMA and PMo3- anions. Long solvophilic PB chains stabilized the PDMAEMA/H3PMo aggregates in solution and reliably prevented macrophase separation. The choice of solvent is crucial. It appears that all three components, both blocks of the diblock copolymer as well as H3PMo, have to be soluble in the same solvent which turned out to be tetrahydrofuran, THF. Evaporation induced self-assembly resulted in highly ordered inverse hexagonal nanocomposite films as observed from transmission electron microscopy and small-angle X-ray scattering. This one-pot synthesis may represent a generally applicable strategy for integrating polyoxometalates into functional architectures and devices.