Biodegradable and biocompatible materials are the basis for tissue engineering. As an initial step for developing bone tissue engineering scaffolds, the in vitro biocompatibility of degradable and bioactive composites consisting of polyhydroxybutyrate-co-hydroxyvalerate (PHBV) and wollastonite (W) was studied by culturing osteoblasts on the PHBV/W substrates, and the cell adhesion, morphology, proliferation, and alkaline phosphatase (ALP) activity were evaluated. The results showed that the incorporation of wollastonite benefited osteoblasts adhesion and the osteoblasts cultured on the PHBV/W composite substrates spread better as compared to those on the pure PHBV after culturing for 3 h. In the prolonged incubation time, the osteoblasts cultured on the PHBV/W composite substrates revealed a higher proliferation and differentiation rate than those on the pure PHBV substrates. In addition, an increase of proliferation and differentiation rate was observed when the wollastonite content in the PHBV/W composites increased from 10 to 20 wt%. All of the results showed that the addition of wollastonite into PHBV could stimulate osteoblasts to proliferate and differentiate and the PHBV/W composites with wollastonite up to 20 wt% were more compatible than the pure PHBV materials for bone repair and bone tissue engineering.