This work presents the application of an electroactive polymelamine-modified screen printed carbon electrode (polymelamine-SPCE) for free chlorine (free-Cl) detection. It is based on EC’ mechanism for electrocatalytic detection of free-Cl with the azo (i.e.,NN) functionality of polymelamine first reduced electrochemically followed by oxidization with free-Cl in a cyclic manner. The polymelamine-SPCE showed a wide linear range from 10 μM to 7 mM (R2 = 0.9957) and a detection limit of 5.5 μM (S/N = 3) for free-Cl detection by flow injection analysis in neutral media. It was successfully demonstrated for the determination of free-Cl in swimming pool and tap waters.