Background: Toxoplasmosis is one of the most important cosmopolitan life-threatening diseases in immune-compromised patients. It is caused by an intracellular protozoon: Toxoplasma gondii (T. gondii), this parasite can cause pneumonia, encephalitis or disseminated disease in immune-deficient patients.
Objectives:  This study aimed to evaluate the prevalence of toxoplasmosis in Egyptian cancer patients and to correlate the prevalence with type of malignancy and the different cancer treatment modalities.
Patients and Methods:  This study conducted on 100  cancer patients (21 male and 79 female) who  attended the  Oncology Outpatient Clinic of Qena University  Hospital and diagnosed by cancer , receiving chemotherapy or  both chemotherapy and radiotherapy, and  their ages ranging from 20 year to 76 years from January 2019 until December2020.
Results: The high incidence of Toxoplasmosis was  among cancer breast patient.  The mean of Ig M titre is 0.849 with minimum level is 0.15 and maximum level is 10.43. There were 70 cancer patients undergoing chemotherapy, 6 of them were positive for toxoplasma Ig M (8.7%) , but 30 of whom received chemotherapy and radiotherapy, 11 of whom were infected (36.7%) according to the IgM level.  
Conclusion: Patients with a positive result are at risk of reactivation of the infection, while patients with a negative result should be informed to prevent primary infection.