<p>Marine-derived nanocarriers represent an emerging interface between marine pharmacology and nanotechnology for immunomodulatory drug delivery. The marine ecosystem provides diverse bioactive compounds, such as polysaccharides, peptides, lipids, proteins, and alkaloids, many of which possess inherent immunoregulatory activity. When incorporated into nanoscale delivery systems such as polymeric nanoparticles, liposomes, micelles, hydrogels, and exosome-like vesicles, these bioactive compounds may exhibit improved stability, bioavailability, controlled release, and targeting efficiency. This review summarizes major classes of marine-derived nanocarriers and discusses their immunomodulatory mechanisms, including pattern recognition receptor activation, oxidative stress modulation, macrophage polarization, dendritic cell maturation, cytokine regulation, and intracellular signaling pathways. Their applications in autoimmune disorders, infectious diseases, vaccine delivery, and cancer immunotherapy are also reviewed. Despite promising preclinical evidence, clinical translation remains limited by challenges related to scalable production, batch-to-batch reproducibility, long-term stability, tissue-specific targeting, safety evaluation, and regulatory approval. Overall, marine-derived nanocarriers offer promising platforms for immunomodulatory drug delivery, but further mechanistic, comparative, and translational studies are required to establish their clinical relevance.</p> Graphical Abstract <p></p>