Intravascular large B-cell lymphoma is a rare Bcell lymphoma subtype characterized by tumor cells found exclusively within vascular lumina. We report the case of an 88-year-old woman who initially presented with pain, swelling, and loss of vision in her left eye. A left orbital mass was revealed by computed tomography, and a biopsy was performed. On histologic examination, large atypical lymphoid cells were present in blood vessel lumina of the intraorbital adipose tissue. No tumor cells were seen in the surrounding tissue. By immunohistochemistry, the tumor cells were positive for CD20, BCL-2, Bcl-6, and CD5; they were negative for CD10 and cyclin D1. Ki-67 revealed a proliferation rate of approximately 80-90%, and CD31 highlighted the vascular endothelium. These findings confirmed the diagnosis of intravascular large B-cell lymphoma. Results of bone marrow and cerebrospinal fluid examinations were negative for involvement, and there was no radiographic evidence of systemic disease.The patient received systemic treatment with etoposide, doxorubicin, vincristine, cyclophosphamide, prednisone, and rituximab in addition to intrathecal methotrexate. The patient had resolution of her intraorbital mass. While it is understood that this disease can involve any organ, only very rarely does intravascular large B-cell lymphoma present with primary ophthalmologic symptoms. Additionally, this patient's disease initially appeared to be isolated, with no skin manifestations or other systemic involvement. To our knowledge, this is the first reported case in which this disease manifested as an isolated intraorbital mass without detectable involvement of any other organ.