Intravascular lymphoma (IVL) is a rare form of non-Hodgkin lymphoma characterized by proliferation of malignant lymphoid cells limited to the lumen of small vessels. Clinical manifestations are nonspecific and result from vascular obliteration and hypoxia. The disease affects primarily the skin and central nervous system, often associated with rapid systemic dissemination and aggressive clinical course if appropriate therapy is not initiated early. Involvement of the lungs, kidneys, adrenal glands, and prostate may occur. Primary pulmonary IVL is exceedingly rare. We describe a case of primary pulmonary IVL in an HIV-positive man presenting with nonspecific constitutional symptoms. High-resolution computed tomography demonstrated centrilobular nodules with ground-glass attenuation and peribronchial ground-glass opacities. The diagnosis was confirmed by thoracoscopic biopsy and histologic findings consisted of accumulation of malignant lymphocytes within alveolar capillaries, pulmonary veins, and peribronchial arterioles. Immunohistochemistry confirmed positivity for CD20, a marker for B lymphocytes. Combined systemic chemotherapy including rituximab was started and resulted in significant clinical and radiologic improvement with long-term disease-free survival.