Background: Intravascular lymphoma (IVL) is an uncommon disease characterized by atypical lymphoid cells growing inside the lumina of small vessels. The diversity of clinical presentation due to possible involvement of multiple organs often complicates its diagnosis. Case Report: Here, we report on a case of IVL with rapidly progressive dementia and Coombs-negative hemolytic anemia. Interestingly, the erythrocytes exhibited a decreased osmotic resistance. Bone marrow histopathology revealed increased erythropoiesis and, finally, a small monoclonal B lymphocyte population. Cerebral magnetic resonance imaging (MRI) demonstrated few micro-bleedings. Computed tomography (CT) showed bilateral ground-glass opacity of the lungs. Within a few days, the patient developed respiratory failure and died. On post-mortem examination, intravascular large B-cell lymphoma with almost complete infiltration of the brain and lungs was diagnosed. Conclusion: IVL should be considered early in situations of unexplained neuropsychiatric disease along with markedly elevated levels of lactic dehydrogenase, anemia, and hemolysis.