Lipid nanoparticles (LNPs) to deliver messenger RNA (mRNA) have emerged as a transformative strategy in cancer immunotherapy. This chapter explores the pivotal role of LNPs in enabling the efficient and targeted delivery of mRNA for cancer treatment, offering an innovative alternative to traditional therapies. LNPs protect mRNA from degradation, ensure its safe passage into the cytoplasm of target cells, and promote the expression of tumor-specific antigens that can activate the immune system against cancer cells. This chapter covers the fundamental properties of lipid nanoparticles, including their composition, structure, and functional modifications, as well as their mechanism of action in mRNA delivery. It also delves into optimizing LNPs to enhance targeting specificity, reduce toxicity, and improve therapeutic efficacy in cancer immunotherapy. Advances in the design of these nanoparticles, including innovations in surface functionalization and their role in overcoming tumor microenvironment barriers, are discussed. The chapter further examines preclinical and clinical applications of LNP-mediated mRNA cancer vaccines and therapies, highlighting recent successes and case studies. In addition, challenges such as ensuring efficient delivery, managing off-target effects, and addressing potential immune reactions are explored. Finally, future perspectives on developing more advanced LNPs and mRNA therapies, including their potential for personalized cancer treatments, are discussed. By providing an in-depth understanding of the current state and future potential of LNP-mediated mRNA delivery, this chapter aims to offer valuable insights into how this technology is shaping the future of cancer immunotherapy.