Herbs including Curcuma longa, Houttuynia cordata, Prunus mume and Rubus coreanus have potential immune enhancing and antimicrobial effects. Probiotics also have antibacterial effects and some are important in regulating the immune system. The aims of the present study were to evaluate the immune enhancing effects of probiotic fermented tetra-herbal combination (PFH) in broiler chicks, and to demonstrate the prophylactic effect of PFH against Salmonella Gallinarum in experimentally infected broiler chicks as initial step towards the development of feed supplements for the promotion of immune activity and disease prevention. Continuous ingestion of PFH markedly increased lysozyme activity in serum and spleen, peripheral blood mononuclear cell (PBMC) proliferation, the CD4+:CD8+ T lymphocyte ratio in spleen and antibody production level in broiler chicks. Conversely, prostaglandin E2 synthesis in serum and PBMC culture medium of PFH-fed chicks were significantly decreased compared with the control group in a dose-dependent manner. In experimentally S. Gallinarum infected chicks, mortality was delayed in 2% PFH-fed chicks. Moreover, survival rates in the 2% PFH-fed group remained the highest among all the trial groups throughout the experimental period. Taken together, these findings suggest that PFH enhances immune activity in broiler chicks and increases survivability against Salmonella Gallinarum in experimentally infected broiler chicks, likely because of potent stimulation of nonspecific immune responses.