Chronic hepatitis B virus (HBV) infection can result in hepatocellular carcinoma (HCC), which is the third leading cause of cancer-related deaths worldwide. For autologous immunotherapy of HCC, patient-derived T cells can be engineered to target HBV-specific antigens by exogenous expression of HBV-specific T cell receptors (TCRs). In contrast to viral delivery methods that can be expensive, time-consuming, inefficient, and potentially toxic during treatment due to the long-lived survival of transduced cells, non-viral mRNA electroporation is a transient, cheaper, and potentially safer alternative. However, high efficiency of transfection, high cell viability, and scalability are important parameters for commercial production of quality, clinically-functional engineered cells. Here, we demonstrate seamless optimization of electroporation conditions for efficient and scalable electroporation of activated primary T cells with HBV-specific TCR mRNA at a scale up to 3.9 billion cells. Moreover, T cells could be cryopreserved soon after electroporation and yielded TCR expression and functional cytokine expression comparable to freshly- electroporated T cells upon thawing. This study demonstrates a robust and efficient manufacturing process for large-scale, transient TCR-expressing T cells with a cGMP-compliant non-viral cell engineering platform.