In clinical trials of adoptive T-cell therapy, the persistence of transferred cells correlates with therapeutic efficacy. However, properties of human T cells that enable their persistence in vivo are poorly understood, and model systems that enable investigation of the fate of human effector T cells (T_E) have not been described. Here, we analyzed the engraftment of adoptively transferred human cytomegalovirus pp65-specific CD8⁺ T_E cells derived from purified CD45RO⁺CD62L⁺ central memory (T_CM) or CD45RO⁺CD62L⁻ effector memory (T_EM) precursors in an immunodeficient mouse model. The engraftment of T_CM-derived effector cells (T_CM/E) was dependent on human interleukin-15, and superior in magnitude and duration to T_EM-derived effector cells (T_EM/E). T-cell receptor Vβ analysis of persisting cells demonstrated that CD8⁺ T_CM/E engraftment was polyclonal, suggesting that the ability to engraft is a general feature of T_CM/E. CD8⁺ T_EM/E proliferated extensively after transfer but underwent rapid apoptosis. In contrast, T_CM/E were less prone to apoptosis and established a persistent reservoir of functional T cells in vivo characterized by higher CD28 expression. These studies predict that human CD8⁺ effector T cells derived from T_CM precursors may be preferred for adoptive therapy based on superior engraftment fitness.