Adult T-cell Leukemia/Lymphoma (ATLL) is a sight- and life-threatening complication of human T-cell lymphotropic virus type 1 (HTLV-1) infection. Ophthalmic manifestations include uveitis, optic nerve oedema, retinal vasculitis, and lymphomatous infiltration. Orbital lesions are rare. We report the case of an orbital tumor revealing systemic ATLL in a 45-year-old Dominican patient who died despite treatment. Apart from late-grade cutaneous T-cell lymphoma, ATLL is the only T-lymphoma to develop in the orbit. Diagnosis is based on serologic evidence of HTLV-1 infection, cytology, and blood sample analysis. Biopsy is deemed necessary. Given the poor prognosis of ATLL and the worldwide presentation of HTLV-1, physicians should consider ATLL in the differential diagnosis of orbital malignant tumor and look for HTLV-1 infection in populations at risk.