Osteoporosis is an age-dependent metabolic bone disease characterized by reduced bone mass. Postmenopausal women with estrogen deficiency are at high risk of developing osteoporosis. This study examined the effects of Gloiopeltis furcata ethanol extract (GFE) on osteoclastogenesis in vitro and ovariectomy (OVX)-induced osteoporosis in vivo. GFE (10∼250 μg/mL) inhibited the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast proliferation and tartrate-resistant acid phosphatase (TRAP) activity. The RANKL-induced protein expression of nuclear factor of activated T cells c1 and TRAP, which are the key transcription factors for osteoclastogenesis, was also decreased by a treatment with GFE. On the other hand, female rats were assigned to five experimental groups: SHAM (sham-operated), OVX-CON (OVX), OVX-GFE20 (OVX+GFE 20 mg/kg/d), OVX-GFE200 (OVX+GFE 200 mg/kg/ d), and OVX-E2 (OVX+estradiol 10 μg/kg/d). After six weeks, an analysis of various bone-related serum parameters showed that the levels of alkaline phosphatase, osteocalcin, TRAP, and RANKL decreased after the administration of GFE. 3D micro-CT analysis showed that the low bone density that developed in the OVX-CON group was reversed in the OVX-GFE20 and OVX-GFE200 groups. H&E and Safranin-O staining revealed less bone destruction in the OVX-GFE groups than in the other groups. Therefore, GFE may serve as a novel therapeutic agent for the treatment of osteoporosis.