Chimeric antigen receptor (CAR) T cell therapy has demonstrated remarkable efficacy in haematological malignancies. However, although viral vector-based methods are effective for CAR T cell manufacturing, they present significant biological, logistical and financial challenges. Non-viral vectors — such as mRNA, transposon and precision genome editors — offer a promising alternative, addressing issues of scalability and cost. mRNA and precision genome-editing technologies hold promise in facilitating the implementation of safe in vivo gene delivery for CAR T cell therapy. In this Primer, we discuss recent advancements in non-viral vectors for CAR immunotherapy, focusing on methodologies, clinical results, opportunities and limitations. We discuss permanent and transient gene engineering technologies, highlighting their ability to efficiently deliver genetic material and perform multiple genetic edits in target effector cells, such as T lymphocytes. We briefly describe delivery methods and preclinical development of ex vivo and in vivo T cell engineering using non-viral vectors. Additionally, we outline key considerations for clinical translation, such as reproducibility and good manufacturing practice. Through a comprehensive review of current literature and clinical trials, we underscore the potential of non-viral vectors to further optimize CAR immunotherapies, paving the way for more advanced and accessible cell-based treatments.