Dolphin Interleukin-10 (IL-10) is a key anti-inflammatory cytokine produced by regulatory T cells, macrophages, dendritic cells, and certain B-cell populations in dolphins, particularly the bottlenose dolphin (Tursiops truncatus), where it plays a central role in limiting excessive immune activation and maintaining immune homeostasis. IL-10 signals through the IL-10 receptor complex (IL-10R1/IL-10R2), activating JAK/STAT3 pathways that suppress pro-inflammatory cytokine production (including IL-1β, TNF-α, and IL-6), reduce antigen presentation, and downregulate Th1-type immune responses. In dolphin health, IL-10 is important in modulating inflammatory responses associated with viral infections such as cetacean morbillivirus and herpesvirus, bacterial pathogens including Brucella spp., chronic dermatitis, pneumonia, and wound healing, where balanced IL-10 expression helps prevent tissue damage while supporting pathogen control. Dysregulated IL-10 responses may reflect immune suppression linked to environmental stressors such as pollutant exposure or harmful algal blooms. As dolphins serve as sentinel species for marine ecosystem health, IL-10 is a valuable biomarker of immune regulation and resilience in both free-ranging and managed populations. In comparative and conservation research, characterization of dolphin IL-10 supports studies of immune tolerance, host–pathogen interactions in marine mammals, environmental immunotoxicology, and cytokine network balance, providing insight relevant to wildlife health and broader mammalian immunology.