To enhance the in vivo antitumor activity of adoptively transferred, CD19-specific chimeric antigen receptor (CAR)–redirected cytotoxic T lymphocytes (CTLs), we studied the effect of restimulating CAR⁺ CTLs through their endogenous virus-specific T-cell antigen receptor (TcR) by the cotransfer of engineered T-cell antigen–presenting cells (T-APCs). Using influenza A matrix protein 1 (MP1) as a model antigen, we show that ex vivo–expanded CD4⁺ and CD8⁺ T-APCs expressing a hygromycin phosphotransferase-MP1 fusion protein (HyMP1) process and present MP1 to autologous human leukocyte antigen (HLA)–restricted, MP1-specific CD4⁺ and CD8⁺ CTL precursors. The MP1-specific CTLs are amenable to subsequent genetic modification to express a CD19-specific CAR, designated CD19R, and acquire HLA-unrestricted reactivity toward CD19⁺ leukemia and lymphoma tumor targets while maintaining HLA-restricted MP1 specificity. The restimulation of MP1×CD19 dual-specific CTLs in vivo by the adoptive transfer of irradiated HyMP1⁺ T-APCs resulted in the enhanced antilymphoma potency of bispecific effector cells, as measured by elimination of the biophotonic signal of established firefly luciferase–expressing Burkitt lymphoma xenografts in nonobese diabetic/severe combined immunodeficiency (NOD/scid) animals compared with control groups restimulated by Hy⁺MP1^neg T-APCs. Engineered T-APCs are a novel and versatile antigen-delivery system for generating antigen-specific T cells in vitro and enhancing the in vivo effector functioning of CAR-redirected antitumor effector cells.