The role of dietary linolenic acid (LN), vitamin E (E) and vitamin C (C) in regulating fish growth and immune response was tested on juvenile darkbarbel catfish Pelteobagrus vachelli. Five dietary combinations were used (-E-LN, +E-LN, -E+LN, +E+LN and -C+E+LN; '+' with addition and '-' without addition) in triplicate. Weight gain was highest in the -E+LN feeding group. Red blood cell in fish fed the +E+LN diet was highest. The haematocrit and haemoglobin of fish fed the -E+LN diet was lowest. Superoxide dismutase, catalase, glutathione peroxidase and glucose-6-phosphate dehydrogenase activities in fish fed the -E+LN diet were higher than those in fish fed other diets. Malondialdehyde in fish fed the -C+E+LN diet was highest. Fish fed the +E+LN diet had higher levels of lysozyme activity, serum protein, complements C3 and C4, and immunoglobulin contents than fish fed other diets. Fish fed the +E+LN diet showed lower mortality and higher antibody titre than fish fed other diets after the fish were challenged with Aeromonas hydrophila for 14 day. This study suggests that the growth of darkbabel catfish is improved by increasing dietary linolenic acids. The diets with high linolenic acid, vitamin E and vitamin C can enhance the immune response and resistance in darkbarbel catfish challenged with A. hydrophila.