The dynamics of a semicrystalline poly(vinylidene fluoride) (PVDF) confined within alumina templates of cylindrical nanopores is studied by means of dielectric spectroscopy. In this study we demonstrate how the counterbalance between spatial confinement and interfacial interactions controls at the nanometer level the dynamic and semicrystalline structure of the polymer. A strong deviation of the relaxation behavior of PVDF embedded within the nanopores is observed as compared to that of the bulk. In particular, the dielectric measurements reveal, for pore sizes of the order of 20 run, the existence of a highly constrained relaxation associated with the polymer-alumina interfacial layer.