This study was conducted to test the efficacy of plum (Prunus mume) and red ginseng (Panax ginseng C.A Meyer) marc as stress inhibitors under heat stress and lipopolysaccharide (LPS) challenge in broilers by investigating their effects on blood biochemical parameters, immunoglobulin concentration and splenic cytokine mRNA expressions. A total of one hundred ninety-two 1-d-old male broiler chicks (Ross 308) were divided into 2 stress conditions (heat and LPS) experiments. Each experiment was divided into 4 treatment groups with 8 replicates of 3 birds in each group. NC (negative control, no immune substances), PC (positive control, 25 ppm β-glucan), PM (1% plum marc) and RGM (3% red ginseng marc) treatments were administered with respective substance through water supplementation. During heat stress, The Ca/Mg ratio in PM and RGM was significantly decreased in comparison with that of NC (P<0.05). The immunoglobulin M was significantly lower in PM than in NC (P<0.05). Expression patterns of splenic cytokine mRNAs (IL-1, IL-2 and IL-6) were similar over the treatment. Expression rates of IL-1 and IL-2 in PM were significantly decreased in comparison with NC. Also, expression rates of IL-1, IL-2 and IL-6 were significantly lower in RGM than in NC (P<0.05). In conclusion, the dietary supplementation of plum and red ginseng marc improved coping ability to heat stress by preventing Ca/Mg ratio increment and by inhibiting inflammatory response in broiler chicks. However, it is necessary to determine optimal dietary level of red ginseng marc for improving growth performances in broiler chickens. These results suggest the possibility that plum and red ginseng marc could be used as the stress inhibitor under heat stress and inflammatory response in broiler chicks.