Background: Clinical features and treatment outcomes of intravascular large B-cell lymphoma (IVLBCL) have rarely been reviewed due to its rarity and pathologic obscurity. Methods: We analyzed 20 patients who were pathologically diagnosed with IVLBCL at the Samsung Medical Center. Results: Initial manifestations were nonspecific, such as fever with cytopenia, elevated serum lactate dehydrogenase and hypoalbuminemia. Hemophagocytosis was frequent and bone marrow was the most common site of pathologic diagnosis in our series. Hepatosplenomegaly, pleural effusion and ground-glass opacity in the lungs were also commonly found, and positron emission tomography imaging showed increased 18F-fluorodeoxyglucose uptake in the involved organs. All patients received CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone) or rituximab-CHOP. The median overall survival (OS) was 38.9 months (95% confidence interval 6.7-71.1). Rituximab-containing chemotherapy compared to chemotherapy alone resulted in higher 3-year OS (71.4 and 25.0%; p = 0.027). Patients with hemophagocytosis had a poorer 3-year OS compared to patients without hemophagocytosis (29.6 and 75%; p = 0.046). Prognostic factor analysis showed the association of pleural effusion with worse OS (p = 0.002). Conclusions: Treatment with rituximab-containing chemotherapy can improve the treatment outcome of IVLBCL. Pleural effusion may be a poor prognostic factor in patients with IVLBCL.