Osteoporosis is a major skeletal disease associated with loss of estrogen in postmenopausal women. In this study, Lactobacillus paracasei subsp. paracasei NTU 101 (NTU 101F) and Lactobacillus plantarum NTU 102 (NTU 102F) were used as starters to ferment soy skim milk. This was then used as a nutritional supplement for 8 weeks to ovariectomized (OVX) mice. This study reveals that soy skim milk fermented with lactobacilli can increase the contents of aglycone isoflavones, soluble calcium, and vitamin D₃. The trabecular bone volumes and trabecular number of the distal femur in mice fed NTU 101F increased by a factor of 1.48 and 1.74 compared with the OVX group. The bone network density and thickness of the distal metaphyseal trabecular in mice fed NTU 101F and Fosamax was significantly greater than that of OVX mice. These results suggest that fermented soy skim milk can attenuate bone loss in OVX mice and lower the risk of osteoporosis.