An electronic component includes external electrodes formed on a base member, each external electrode including a plurality of layers of which the outermost layer is a tin plating layer. The tin plating layer has a polycrystalline structure, and atoms of a metal other than tin are diffused into the tin crystal grain boundaries. Alternatively, each external electrode includes a plurality of layers including a thick-film electrode formed on the base member, a nickel layer or a nickel alloy layer formed on the thick-film electrode and a tin plating layer formed on the nickel layer or the nickel alloy layer. The tin plating layer has a polycrystalline structure and nickel atoms are diffused into the tin crystal grain boundaries. Methods for fabricating electronic components and a circuit board provided with a plurality of electronic components are also disclosed.