First-generation messenger RNA (mRNA)-lipid nanoparticle (LNP) vaccines have demonstrated clinical efficacy; however, the magnitude and durability of the immune responses they elicit remain suboptimal. Here, we have employed innovative strategies to engineer mRNA-LNP vaccines that specifically exploit the biology of conventional type 1 dendritic cells (cDC1s). First, we developed mRNA-LNPs encoding immune-modulatory molecules and identified transcription factor-encoding mRNA-LNPs (mRNA-LNP-TFs) capable of reprogramming cDC1-like cells in vivo. Coadministration of mRNA-LNP-TFs with low doses of antigen markedly enhanced CD8+ T cell immunity, resulting in improved vaccination outcomes in models of bacterial infection and tumour clearance. Second, we directly targeted mRNA-LNPs to cDC1s or to both cDC1s and cDC2s. To achieve this, we generated antibody-conjugated mRNA-LNPs directed against receptors highly expressed on these dendritic cell subsets. Targeted delivery significantly increased mRNA-LNP uptake and mRNA expression in cDC1s and cDC2s following both intramuscular and intravenous administration. These DC-targeted mRNA-LNPs were engineered either to enhance DC immunogenicity or, alternatively, to induce DC killing and depletion. In summary, mRNA-LNPs provide a versatile platform for manipulation of DC biology, enabling more sophisticated and effective immunotherapeutic vaccination strategies.