This study investigated the effects of dietary supplementation with hot water extracts (HE) of selfheal (Prunella vulgaris) and Lactobacillus rhamnosus culture fluid (LF) on the growth and non-specific immune responses of juvenile olive flounder. A total of 270 fish ($5.07{pm}0.01g$, average $weight{pm}SD$) were divided randomly into nine groups, and three groups were fed one of three isonitrogenous (51% crude protein) and isocaloric (17.6 MJ/kg) diets. The diets contained no supplement, 50 mL hot water extract, or 50 mL L. rhamnosus fluid (designated as diets CON, HE and LF, respectively). During the 8-week feeding trial, the growth, feed utilization and survival of the fish were not significantly affected by the experimental diets. There were no significant differences in the hematocrit and hemoglobin of fish fed each of the experimental diets. However, the serum alanine aminotransferase and aspartate aminotransferase activity were lower with the dietary supplements containing HE and LF. The alanine aminotransferase activity of fish fed the HE diet was significantly lower than that of fish fed the control diet. The hematocrit, hemoglobin, and nitroblue tetrazolium (NBT) activity were higher 3 hr after feeding than 24 hr afterwards. The NBT activity of fish fed the HE and LF diets were significantly higher than that of fish fed the control diet 3 hr after feeding. The findings suggest that dietary supplementation with HE and LF could enhance the nonspecific immune responses of juvenile olive flounder.