A tool holder includes a main body, a back cover and a supporting portion. The main body has a first end formed with a hanging portion and t a second end. The back cover is pivoted to the second end and is closable or expendable relative to the main body to make an inner surface thereof selectively cover or uncover one said side face of the main body. The supporting portion is movably disposed between the main body and the back cover. When the back cover is closed, the supporting portion is received between the main body and the back cover; and when the back cover is expended, two ends of the supporting portion are positionably disposed on the main body and the back cover respectively and the main body and the back cover are positioned relative to each other.