Blends of poly(3-hydroxybutyrate) (PHB)/poly(methylene oxide) (POM) were prepared by melt mixing and subsequent compression moulding. Crystallization, thermal behaviour, morphology and mechanical properties of the blends were studied by using differential scanning calorimetry, optical and scanning electron microscopy, and dynamic-mechanical analysis. The immiscibility of the two polymers in the liquid state was demonstrated. Moreover, two distinct spherulitic phases were evidenced in the solid state and changes of the texture structure with the composition were also observed. Finally, tensile and impact tests were carried out in order to establish the mechanical behaviour of the blends.