Several studies have shown that alpha-ketoglutaric acid (AKG) increases serum levels of proline and has beneficial effects on skeletal development. We studied the effect of alpha-ketoglutaric (AKG) acid calcium salt (6 g AKG and 1.68 Ca/day) or calcium alone (1.68 Ca/day) on serum C-terminal cross-linked telopeptide of type I collagen (CTX) and osteocalcin (OC), as well as on lumbar spine bone mineral density (BMD) in a randomized, parallel group, double-blind, 6-month study conducted on 76 postmenopausal women with osteopenia. The maximum decrease of the mean CTX level in the AKG-Ca group was observed after 24 weeks (37.0%, p = 0.006). The differences in CTX between study groups were statistically significant after 12 and 24 weeks. The OC serum level was not affected by treatments. The BMD of the AKG-Ca group increased by 1.6% from baseline; however, the difference between treatment groups was estimated as 0.9% (non-significant). This study suggests the potential usefulness of AKG-Ca in osteopenic postmenopausal women. AKG-Ca induced beneficial changes in serum CTX, which was consistent with preserving the bone mass in the lumbar spine; however, the long-term effect needs to be further investigated.