Large granular lymphocyte leukemia (LGL) is a clonal, lymphoproliferative disorder with an indolent disease course. T-cell LGL (T-LGL) is the most common type of LGL driven from T-cell lineage (85%). The coexistence of T-LGL with several types of autoimmune disorders, mostly rheumatoid arthritis (RA), has been reported. Felty's syndrome (FS) is defined by splenomegaly, low neutrophil count, and destructive arthritis and is usually seen in <1% of patients with RA. About 30% to 40% of patients with FS have been reported to have an expansion of large granulated lymphocytes in the circulation. FS and T-LGL are similar in terms of clinical manifestations, response to immunosuppressive therapy, their smoldering course, and immunogenetic findings, proposing FS and T-LGL with RA might be different aspects of a single disease spectrum. In this article, we present a case with long-standing RA who had never been on DMARD (Disease Modifying Anti-Rheumatic Drugs) treatment found to have constitutional symptoms, neutropenia, and splenomegaly, and the patient was diagnosed with T-LGL.