The invention provides modified Natural Killer (NK) cells expressing an antigen-specific functional T cell receptor (TCR) complex. These NK cells are used for T cell receptor (TCR) gene therapy in order to circumvent any risk of mispairing of the TCR a and β chains and to provide Major Histocompatibility Complex (MHC)-restricted antigen-specific cytotoxicity to the NK cells. The invention additionally provides methods for producing the modified NK cells, therapeutic compositions including the modified NK cells, and methods for using the modified NK cells in therapy of cancer, viral infections, autoimmunity, and graft versus host disease (GvHD).