An overvoltage protection circuit and a portable electronic device having the same are introduced. The overvoltage protection circuit provides overvoltage protection when an input voltage exceeds a rated voltage tolerable by an internal circuit unit in the portable electronic device. A reference voltage and a partial voltage are generated from the input voltage through a voltage limiting unit and voltage dividing module, respectively, and conveyed to a comparing module for comparison. Comparison of the reference voltage and the partial voltage is followed by generation of a switch signal whereby a switch unit determines whether to apply the input voltage to the internal circuit unit. The voltage dividing module sets the maximum rated voltage tolerable by the internal circuit unit and enables the overvoltage protection circuit to give overvoltage protection to the portable electronic device regardless of temperature.