The dynamics of poly(ethylene oxide) (PEO) intercalated in the subnanometer-spaced graphite oxide (GO) layers is investigated by using broadband dielectric spectroscopy (BDS). To this end, we compare BDS data obtained for PEO chains of increasing lengths, from three monomeric units to several thousand repetitive ethylene oxide units (n = 3-2135). Two relaxations were clearly identified for the confined PEO. The slowest one is proposed to originate from interfacial polarization. It is dependent on the chain length and exhibits a change in activation energy at 247 K, a temperature at which the GO exhibits an interlayer expansion when subjected to an increase in temperature. The fastest relaxation is nearly independent of the chain length, in contrast to the behavior that we found for the beta-relaxation of bulk PEO. These results strengthen a previous hypothesis suggesting the emergence of a new set of chain length scales primarily dictated by the presence of anchoring points on the GO substrate upon intercalation. Additionally, the fastest relaxation exhibits a crossover at 175 K, which indicates the coexistence of two distinct processes, one occurring with the same activation energy as in the bulk polymer, and the other with lower activation energy. The latter is probably associated with the planar zigzag conformation in the confined PEO as previously determined by high-resolution inelastic neutron scattering.