The emergence of mRNA-based cancer immunotherapy has transformed the avenue of cancer treatment, offering an innovative strategy that leverages the body's immune system to identify and eradicate tumor cells selectively. Effective delivery of mRNA to specific organs and cells is limited by its instability, low cellular uptake efficiency, and degradation during extracellular transport and endosomal escape. Significant advancements in nanoparticle design have driven the rapid progress of mRNA-based immunotherapies. Nanocarriers have emerged as vital delivery systems, providing enhanced stability, resistance to enzymatic degradation, and efficient mRNA delivery to target cells. This chapter investigates the design, synthesis, and functionalization of different types of nanoparticles, including lipid-based, polymeric, and hybrid nanoparticles and also highlights their unique characteristics and mechanisms for mRNA delivery in cancer immunotherapy. This chapter explores cellular uptake mechanisms, strategies for endosomal escape, and the subsequent translation of mRNA into therapeutic proteins that elicit a vigorous anti-tumor immune response. Recent advances in nanoparticle-based mRNA vaccines are also explored, with an emphasis on research findings and clinical trials that reveal both their potential and challenges. The chapter aims to provide a thorough overview of nanoparticle integration in mRNA-based cancer immunotherapy and also offer insights into future developments and emerging trends in the field.