Low oxygen availability is known to activate the hypoxia-inducible factor-1 alpha (HIF-1 alpha) pathway, which is involved in the impairment of fracture healing. However, the role of low oxygen in fracture healing remains to be fully elucidated. In the present study, rats were divided into two groups and treated with CoCl2 or saline, respectively. Rats with tibial fractures were sacrificed at 14, 28 and 42 days subsequent to fracture. Autoradiography was performed to measure healing of the bone tissue. In addition, the effects of cobalt chloride (CoCl2) on the expression of two major angiogenic mediators, HIF-1 alpha and vascular endothelial growth factor (VEGF), as well as the osteoblast markers runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP) and osteocalcin (OC) were determined at mRNA and protein levels by reverse transcription-quantitative polymerase chain reaction, western blot analysis and immunohistochemistry. Systemic administration of CoCl2 (15 mg/kg/day intraperitoneally) significantly promoted fracture healing and mechanical strength. The present study demonstrated that in rats treated with CoCl2, the expression of HIF-1 alpha, VEGF, Runx2, ALP and OC was significantly increased at mRNA and protein levels, and that CoCl2 treatment enhances fracture repair in vivo.