Toxoplasma gondii (T. gondii) is an opportunistic parasite. Transmission from T. gondii-infected donors to recipients is possible through blood and organ transplantation. In this study, it was aimed to investigate the presen ce of T. gondii antibodies in healthy donors and in blood recipients with immunosuppressed hematological malignancies. A total of 92 patients included in the present study (46 donors and 46 patients). Sixteen of the hematological patients had lymphoblastic leukemia and 14 had acute myeloblastic leukemia. The presence of IgG and IgM Toxoplasma antibodies and IgG avidity values were investigated by ELISA. Twenty-two (47.8%) of patients and 11 (23.9%) of the donors were found to be positive for T.gondii IgG antibodies. IgG positivity was detected in all patient groups except those with aplastic anemia. The highest IgG positivity was found in acute myeloblastic leukemia (8) and lymphoblastic leukemia (5). IgM seropositivity was detected totally three cases (3.3%), two of 46 patients (4.3%) and one 46 of donors (2.2%). Although the number was low, all patients with chronic myeloid leukemia were detected both IgG and IgM positive (100%). Low avidity was found in all three of the IgM positive cases. Considering that toxoplasmosis is an infection that causes severe clinical symptoms and death, routine diagnostic methods that detect the presence of parasites in donor and patient groups will be beneficial for the prevention of T.gondii transmission.