To improve the health benefits of ginseng flower buds via microbial fermentation, we evaluated the ginsenoside content and in vitro immune-stimulating activities. The flower buds were grouped as control (non-fermented) and those fermented by Bacillus subtilis (FBS), Lactobacillus plantarum (FLP), Lactobacillus casei (FLC), Candida utilis (FCU), Saccharomyces cerevisiae strain CHY1011 (FY1), S. cerevisiae strain ZP541 (FY2), and a mixed strain culture using L. plantarum, L. casei, and C. utilis (FM). Total ginsenoside content in FBS increased higher than that of the control. The expression of IL-1β was found to be higher than that of the control following stimulation by FBS and FY1. IL-2 gene expression was high in FM, and TNFSF14 gene expression increased in FCU- and FY1-treated cells. Considering the differences in the quantities and composition of the ginsenoside, other various polysaccharides or phenolic compounds in fermented ginseng flower-buds would indicate the difference in the activation of immune response.