The anti-obesity effects of fermented black bean were tested with mice fed a high fat diet for seven weeks. Body weight gain and feed efficiency ratio (FER) in the high fat diet control (HC) group were markedly higher, compared with those of the normal control (NC) group, but were significantly lower in the 2% black bean powder supplemented high fat diet (BB) group and 2% black bean powder fermented by M. pilosus supplemented high fat diet (BBM) group, compared with those of the HC group. Food intake in the HC and BB groups was significantly lower than that of the NC and BBM groups. Water intake in the HC group was significantly lower than that of the NC group, but was higher in the BB and BBM groups, compared with that of the HC group. On the other hand, relative liver and kidney weight in the HC group was lower than that of the NC group, but was higher in the BB and BBM groups, compared with that of the HC group. In addition, whereas epididymal fat weight in the HC group was markedly higher than that of the NC group, it was significantly lower in the BB and BBM groups, compared with that of the HC group. Meanwhile, hepatic GSH in the HC group was significantly lower than that of the NC group, but was slightly higher in the BB and BBM groups, compared with that of the HC group. Although hepatic LPO in the HC group was dramatically higher than that of the NC group, it was significantly lower in the BB and BBM groups, compared with that of the HC group. In addition, serum TG, total cholesterol, and LDL-cholesterol in the HC group was significantly higher than that of the NC group, but was significantly lower in the BB and BBM groups, compared with that of the HC group. On the contrary, HDL-cholesterol in the HC group was significantly lower than that of the NC group, but was higher in the BB and BBM groups, compared with that of the HC group. In addition, activity of XOR D type in the HC group was lower than that of the NC group, but was slightly higher in the BB and BBM groups, compared with that of the NC group. Activities of ROS scavenging enzymes, such as SOD, GPX, and GST in the HC group were significantly lower than those of the NC group, but were significantly higher in the BB and BBM groups, compared with those of the HC group. In addition, serum ALT activity in the HC and BB groups was higher than that of the NC group, but was significantly lower in the BB and BBM groups, compared with that of the HC group. In histopathological findings, hepatic fat accumulation in the HC group was higher than that of the NC group, but was lower in the BBM group, compared with that of the HC and BB groups. In particular, antiobese, hypolipidemic, and antifatty liver effect of black bean powder fermented by M. pilosus was specifically higher than that of non-fermented steamed black bean. In conclusion, the constituents of black bean fermented by Monascus pilosus have been proven to not only inhibit obesity and hyperlipidemia but also decrease hepatic fat accumulation in high fat diet-induced obese mice.