Toxoplasmosis is a zoonotic disease caused by Toxoplasma gondii that is prevalent in humans and animals. This study was aimed to determine the seroprevalence of T. gondii infection among hemato-oncology patients and its association with sociodemographic and behavioural characteristics. This cross-sectional study was conducted at the Hospital Universiti Sains Malaysia (USM) involving 56 blood samples from hemato-oncology patients. Anti-T. gondii IgG and IgM antibodies and IgG avidity were determined using enzyme-linked immunosorbent assays (ELISA). The association of T. gondii exposure, sociodemographic, and behavioural characteristics were assessed by a questionnaire and face-to-face interviews. Twenty-eight (50%) patients were seropositive for T. gondii antibodies, where 27 (48.21%) patients were IgG+/IgM- and one patient (1.79%) was IgG+/IgM+ with high avidity index, indicating infection of more than 20 weeks. A univariate analysis showed that age, gender, ethnicity, marital status, educational level, employment status, stem cell transplant, blood transfusion, close contact with cats, water supply, and consumption of undercooked meat were not significantly associated with Toxoplasma seropositivity (p < 0.05). Our study has demonstrated, for the first time, the serological evidence of T. gondii exposure among hemato-oncology patients in Hospital USM. Our findings indicated that latent toxoplasmosis was relatively prevalence among our patients. Therefore, serological screening tests should be considered for immunocompromised patients as well as the implementation of health education programmes to encourage a healthy lifestyle and the consumption of healthy food among them.