Many heavy metals are essential as trace nutrients for living organisms. These essential heavy metals can also cause toxicity at high levels. Plants have evolved a range of homeostasis mechanisms to minimize the harmful effects and maintain the concentration of essential metals within physiological limits. In Arabidopsis thaliana, two copper chaperones, antioxidant protein 1 (ATX1) and ATX1-like Cu chaperone (CCH), share high sequence homology. The molecular mechanism involved in copper homeostasis was proposed. However, the biological importance of CCH and ATX1 in plants remains unknown. In this study, genetic and physiological approaches were employed. We demonstrate that ATX1 plays an essential role in copper homeostasis in conferring tolerance to excess copper and copper deficiency. The high Cu accumulation and tolerance of ATX1 overexpression lines with high concentration of Cu in the soil suggest the possible use of ATX1 for phytoremediation of Cu contaminants.