Listeriosis is an infectious disease caused by Listeria monocytogenes microorganisms. A human can catch an infection through fecal-oral, aerogenous, or transplacental route. The listeriosis incidence in Ukraine is sporadic, single cases are not related to each other. Listeriosis is characterized by a high rate of mortality and polymorphism of clinical manifestations. The symptoms of the disease are multiple-organ: damage to the central nervous system, septic symptoms, aborts, mastitis; listeriosis can also be subclinical. The disorders of the central nervous system are associated with meningitis, meningoencephalitis, or brain abscess. The importance of the problem of diagnosis and treatment of listeriosis derived from the disease sporadicity, polymorphism of its manifestations, difficulties in etiological verification of the diagnosis. The case described is specific due to the diagnostic mistake: a child was not diagnosed with sepsis. Listeriosis in this child had a progressive course with sepsis development. Listeriosis is a rare infection, therefore it was difficult to suggest this particular infection intra vitam.