Recently, the use of natural immunopotentiators, such as plant extracts, is predicted to offer high disease-prevention potential in aquaculture. However, few reports on the immunomodulatory impacts of olive extract (OE) on teleost are available. Therefore, the effects of dietary intake of triterpene-enriched OE on black sea bream ( Acanthopagrus schlegelii) were investigated in this study. Our data showed that total blood cell counts, in vivo content of lysozyme, activities of antiprotease and myeloperoxidase, and contents of IL-4 and IL-6 were significantly up-regulated by dietary intake of triterpene-enriched OE. Additionally, the hampered immune response induced by cadmium exposure was significantly mitigated by the administration of OE as were indicated by partially or completely rescued immune-relating parameters. Furthermore, the expressions of immune-related genes encoding NF-κB inhibitor alpha (IkBα), tumor necrosis factor α (TNFα), cyclooxygenase-2 (COX-2), and proto-oncogene protein c-fos (FOS) were found to be significantly up-regulated by the dietary intake of OE. In general, the results suggested that the dietary intake of triterpene-enriched OE has immune enhancing effect in black sea bream. Such effect may be realized by 1) increasing the total counts of diverse blood cells; 2) activating nonspecific immune biomolecules; and 3) affecting signaling pathways such as IKK and ERK and subsequently inducing IL-4 and IL-6 biosyntheses.