The authors present the case of a 33-year-old woman presenting with a 4-week history of vertigo and headaches. Physical examination revealed an isolated static cerebellar syndrome. Magnetic resonance imaging showed a homogeneously enhancing tumor located in the fourth ventricle. Complete surgical removal was performed and microscopic examination revealed a high-grade B-cell lymphoma. Postoperative investigations confirmed it to be primary. Only one case of primary isolated lymphoma of the fourth ventricle has been briefly reported in the medical literature. The authors suggest that primary lymphoma must be considered in the list of fourth ventricle tumors.