Dendritic cells (DCs) are the most potent antigen-presenting cells (APCs) and play a crucial role in antitumor immunity. Consequently, various strategies have been explored to utilize DCs as therapeutic vaccines, leveraging their ability to target tumor cells. A variety of antigen formulations were tested to evaluate their efficacy in vaccination, including purified tumor-associated antigens, synthetic polypeptides, and mRNA encoding tumor-associated antigens or neoantigens. In this protocol, we describe the ex vivo generation of dendritic cells from peripheral blood mononuclear cells and loading with in vitro transcribed mRNA for vaccination purposes under Good and Manufacturing Practices.