Toxoplasmosis is a widespread parasitic disease. It is caused by an intracellular parasite Toxoplasma gondii. It can affect various tissues and organs, forming cysts and continuing to replicate within them. In people with intact immune system, tissue cysts remain in latent state throughout their whole life. However, in cases of cellular immunodeficiency the infection can be reactivated, which leads to secondary generalization of the process. People with HIV most commonly present with cerebral toxoplasmosis. Non-specific neuroimaging signs, as well as absence of pathognomonic symptoms and specific laboratory data lead to difficulties of cerebral toxoplasmosis diagnosis, particularly in the cases with a history of multiple sclerosis that has similar clinical symptoms and brain MRI data suggesting of tumefactive multiple sclerosis image. A clinical case of cerebral toxoplasmosis in a female patient with multiple sclerosis and HIV infection is described.