Toxoplasmosis is regarded as one of the most important global life-threatening diseases in immune-compromised people. The intracellular protozoon Toxoplasma gondii is the causative pathogen of toxoplasmosis. Aim of this study is to investigate the possible association between T. gondii infection and breast cancer (BC) in Iraqi women, also to assess the effect of T. gondiion interleukin 10 (IL-10) of the immune response. By ELISA method, blood samples from 81 women with breast cancer and 60 apparently healthy women have been examined for presence of anti-toxoplasmaantibodies, also the levels of serum IL-10 were estimated in these subjects. Results showed that women with BC had the highest prevalence rate of toxoplasmosis. The anti- T.gondiiantibodies was 38.27% for IgG and 4.93% for IgM, while in the control group it was 26.66% and 0.0% respectively, with no significant difference for IgG (P =0.148) and IgM (P = 0.081). A highly significant difference was found in the level of IL-10 between BC women with toxoplasmosis (10.24%) and BC women without toxoplasmosis (3.6%).These findings suggest that incidence rate of T. gondii infection is higher in breast cancer women and higher level of IL-10than their cross-matched control subjects. Therefore, we recommend the inclusion of a screening test for toxoplasmosis and the level of IL-10 in BC patients as in their routine workup.