In this study, Korean mistletoe extract (KM-110) was fermented with two strains of Lactobacillus (FKM-110) and then toxicity, lectin content, and immune activities were investigated. The lectin content of FKM-110 was about 53-71% lower than that of KM-110. When mice were subcutaneously administered with KM-110 and FKM-110, the $LD_{50}$ obtained for KM-110 treatment was 50-100 mg/kg as compared to 150-200 mg/mL for FKM-110. Each preparation stimulated macrophages directly and enhanced productivity of inflammatory cytokines such as TNF-${alpha}$ and IL-$1{eta}$. FKM-110 treatment resulted in lower cytokine production compared to KM-110. When mice were immunized with Keyhol limpet hemocyanin (KLH) antigen along with KM-110 or FKM-110 administration, higher antibody titers to KLH were observed in the KM-110 or FKM-110 groups compared to mice immunized with KLH alone, thereby showing no difference between KM-110 and FKM-110. Therefore, fermentation of Korean mistletoe extract with these Lactobacillus strains decreased toxicity in vivo while the enhancement of immune activity by KM-110 and FKM-110 was similar. These data suggest that KM-110 fermentation tended to decrease lectin content and in vivo toxicity. In addition, other components in the fermented mistletoe extract appear to stimulate immuno-adjuvant activity instead of lectin.