Gamma heavy chain disease (gHCD) is a rare lymphoproliferative disorder characterized by the production of a truncated immunoglobulin heavy chain. Although some cases of gHCD are concurrent with other lymphoid neoplasms, few have been reported. We herein present the case of a 73-year-old woman with gHCD and T-cell large granular lymphocytic leukemia. A multiparameter flow cytometry analysis revealed neoplastic cells that were positive for CD28, a marker of T-cell activation, the anti-apoptotic antigen of neoplastic plasma cells, CD38 and CD45. The results of this multiparameter flow cytometry analysis may contribute to furthering the understanding of the clinicopathological features of gHCD.