The invention relates to a foldable tool set installed with a chain repair tool. The tool set has a housing and foldaway tools pivoted on the housing. The chain repair tool comprises a main body and an ejector pin screwed on top of the main body. The chain repair tool is pivoted on the tool set and can be folded within the tool set or lifted outward. In addition, an arm is included and one end of it is pivoted on one side of the chain repair tool to control movement of the chain repair tool. The chain repair tool and the arm are folded together in the housing. Accordingly, operation of disassembling and reassembling of chains can be conducted with this tool set without any other required tools.