Clinical signs of a disease locally referred to as “unsteady gait disease” for the Tibetan gazelle (Procapra picticaudata) were observed in the Qinghai Lake watershed area, China. The objective of this study was to determine if there was a relationship between the disease and copper (Cu) deficiency. Chemical examinations showed that Cu concentrations in soil and forage samples were similar from areas where gazelles were affected and unaffected. However, concentrations of sulfur (S) and molybdenum (Mo) in the soil and forage samples from the affected area were significantly higher than those from the unaffected areas (P<0.01). Copper concentrations in samples of blood, hair, and liver from the affected gazelles were significantly lower than those in unaffected animals (P<0.01). Supplementation of CuSO₄ in affected gazelles improved their appetite and vigor. We conclude that the disorder of Tibetan gazelles was caused by Cu deficiency, attributable to the high S and Mo content in forage.