Dynamic viscoelastic properties of binary blends consisting of an isotactic polypropylene (i-PP) and ethylene-1-octene copolymer (PEE) were investigated to reveal the relation between miscibility in the molten state and the morphology in the solid state. In this study, PEE with 24 wt % of 1-octene was employed. The PEE/PP blend with high PEE contents showed two separate glass-relaxation processes associated with those of the pure components. These findings indicate that the blend presents a two-phase morphology in the solid state as well as in the molten state. The PEE/PP blend with low PEE content showed a single glass-relaxation process, indicating that PEE molecules were probably incorporated in the amorphous region of i-PP in the solid state. The DMTA analysis showed that the blends with low PEE contents presented only one dispersion peak, indicating a certain degree of miscibility between the components of these blends. These results are in accordance with the results of the rheological analysis.