The objectives of this study were the chemical synthesis of polypyrrole particles, the investigation and estimation of the impact of polypyrrole particle concentration, and the evaluation of the effect of duration of treatment on immune-related haematological parameters and peritoneum cells in mice. The results showed that chemically prepared polypyrrole particles did not have any detectable cytotoxic effect on mouse peritoneum cells. Polypyrrole particles did not induce any allergic response, nor did they affect spleen, kidney or liver indexes. Moreover, no effect of polypyrrole particles on immune-related haematological parameters was observed. No inflammation was detected in the peritoneum of mice after a 6-week period of treatment with polypyrrole particles. In conclusion, chemically synthesized polypyrrole particles showed good biocompatibility in mice and are attractive candidates for biomedical applications in-vivo.