Compatibility of a crystalline/crystalline polymer blend, poly(vinyl alcohol) (PVA)/poly(3-hydroxybutyrate) (PHB), was studied by high-resolution solid-state C-13-NMR spectroscopy. The H-1 T-1 measurement demonstrated that both the compatibility and the domain size depend on the composition of the blend. The PVA/PHB blend is compatible only when the blend contains a large amount of PVA. The domain sizes of the compatible blend are less than 200 Angstrom. In the pulse saturation transfer (PST) MAS NMR spectra, the carbonyl carbon resonance from PHB showed a downfield shift, which indicates that the compatibility of the PVA/PHB blends is due to the hydrogen-bonding interaction in the amorphous phase. The DSC measurement showed that the compatible blends adopt low crystallinity for both PHB and PVA. The crystallization in these blends is likely to be disturbed by the hydrogen-bonding interaction in the amorphous phase. The compatibility of PVA/PHB is also affected by the tacticity of PVA. The compatible composition range of the syndiotactic-rich PVA/PHB blend is wider than that of the atactic-PVA/PHB blend. It is likely that the capacity to form the hydrogen bond depends on the tacticity of PVA.