Objectives: Toxoplasma gondii is a worldwide prevalent zoonotic parasite which causes toxoplasmosis. An appropriate vaccine for animals could interrupt the circle between animals and humans. Our previous study showed that excreted/secreted antigens (E/SA), derived from the peritoneum of mice infected with T. gondii tachyzoites could be considered as a good candidate for animal vaccination. Interleukin-10 (IL-10) inhibits proliferation of B and T lymphocytes and induces homeostasis in immune system responses. However, since IL-10 has also been shown to suppress the killing of T. gondii by human macrophages, the aim of this study was to evaluate IL-10 serum levels after vaccination with T. gondii E/SA prepared in vivo. Methods: T. gondii tachyzoites were inoculated in the peritoneum of mice and harvested E/SA were used as a vaccine, with and without adjuvant, in T. gondii infected and un-infected mice. IL-10 serum levels were evaluated using the ELISA technique. Results: The data showed that although serum levels of IL-10 were not changed at the early phases, they were elevated at the end phases of vaccination with T. gondii E/SA. Conclusion: Based on these and our previous results, it can be concluded that in vivo prepared T. gondii E/SA could be considered as a good candidate for animal vaccination.