An etchant composition is provided comprising 10% to 20% by weight of hydrogen peroxide, 0.1% to 2% by weight of an azole-based compound, 0.1% to 10% by weight of a mineral acid compound, and 0.1% to5% by weight of water surface stabilizer, 0.01 wt% to 0.1 wt% of fluoride, 0.1 wt% to 10 wt% of the sulfate-based compound, and water contained in an amount such that the total weight of the etchant composition is 100 wt%. The etchant composition according to an embodiment of the inventive concept may be used to etch a metal film containing copper and a molybdenum-titanium alloy to form a metal pattern, or to fabricate a thin film transistor substrate.