Polyriboinosinic-polyribocytidilic acid (poly I:C) was administered to turbot, Scophthalmus maximus, via injection, oral route, and immersion. Samples of liver, spleen, and head kidney were individually collected at different time intervals (0, 24, 48, 72, 96, and 120 h) after poly I:C treatments. Transcription levels of Mx, hepcidin, and IgM in the organs of turbot were detected using RT-PCR. It was found that Mx mRNA was significantly induced in the liver, head kidney, and spleen 48-h postinjection with poly I:C, and the effects of immersion and oral route on Mx transcription were analogous to that of injection method. Meanwhile, the hepcidin mRNA was significantly induced in the spleen but not in the liver and head kidney 48-h postinjection. No significant increase of IgM mRNA was found in the liver and spleen after poly I:C challenge. The results indicated that the antivirus state resulted from the Mx expression and could be induced with poly I:C via injection, immersion, and oral methods. The influence of poly I:C on IgM and hepcidin transcription suggested that both innate and adaptive immunity could be modulated through interferon-inducible signaling pathways.