Cell encapsulation can protect cells from the host immune system. It is well‐known that cytotoxic T lymphocytes (CTLs) can destroy cancer cells. In this study, we individually encapsulated CTLs in a cationic polyelectrolyte in combination with two types of nanomaterials: magnetic nanoparticles (MNPs) and gold nanorods (GNRs) conjugated to anti‐human epidermal growth factor receptor‐2 (HER2) antibodies referred to as CTLs/mMNPs/PAH/GNRs@HER2. When MCF‐7 breast cancer cells were co‐cultured with CTLs/mMNPs/PAH/GNRs@HER2 and subjected to a magnetic field and laser irradiation, the viability of MCF‐7 cells was significantly decreased to 42.98 ± 0.57% in comparison to MCF‐7 cells without any treatment or MCF‐7 cells co‐cultured with CTLs (51.52 ± 0.57%). This can be a novel strategy for cancer treatment using encapsulated CTLs in polyelectrolytes and dual nanomaterials in combination with magnetic exposure and laser irradiation.