Bacterially produced polyhydroxybutyrate (PHB) polymer has a lot of potential as an application for environmentally degradable plastics. We aimed in this study to blend PHB with the sernicrystalline polymers poly(vinyl acetate) (PVAc) and poly(vinyl acetate-co-vinyl alcohol) (PACA) to obtain material with better physical properties. We investigated compatibility over a wide composition range using different techniques. Viscosity measurements were used to study polymer-polymer miscibility in dilute solutions with chloroform as cosolvent. The data is discussed according to the viscosity interaction parameters, which are treated as excess properties by similarity with those of real solutions. Dielectric investigations were carried out at different frequencies ranging from 100 Hz to 50 kHz. The obtained data indicated that more than one relaxation mechanism was present, which were ascribed to the rotation of the main chain and its related motions. A glass-transition temperature composition diagram, IR spectroscopy, and a morphological investigation were also used to give more information about the compatibility of such blends. The results of this study indicate that PHB/PVAc is semi-compatible, whereas PHB/PACA is compatible at least in the assayed composition range of hydrolysis. We also extended the study to carry out some biological activity investigations, which were tested against the representative number of pathogenic organisms with the disk diffusion method. The different compositions of the investigated blend were biologically active when compared with the individual polymers.