The tumor suppressor p53 is widely dysregulated in cancer and represents an attractive target for immunotherapy. Due to its intracellular localization, p53 is inaccessible to classical therapeutic monoclonal antibodies, an increasingly successful class of anti-cancer drugs. However, peptides derived from intracellular antigens are presented on the cell surface in the context of major histocompatibility class I (MHC I), and can be bound by T cell receptors (TCRs). Here, we report the development of a novel antibody, T1-116C, that acts as a TCR mimic to recognize an HLA-A*0201-presented wild-type p53 T cell epitope, p5365-73(RMPEAAPPV). The antibody recognizes a wide range of cancers, does not bind normal peripheral blood mononuclear cells, and can activate immune effector functions to kill cancer cells in vitro. In vivo, the antibody targets p5365-73 peptide-expressing breast cancer xenografts, significantly inhibiting tumor growth. This represents a promising new agent for future cancer immunotherapy.