This work reports the inhibition properties of nicotinic acid (NAC) for copper protection during its applications in seawater systems such as water pipelines, shipbuilding, seawater desalination operations and heat exchange systems. The efficiency of nicotinic acid (NAC) as a copper corrosion inhibitor in 3.5 wt % NaCl solution was investigated by Tafel extrapolation and electrochemical impedance spectroscopy (EIS) methods in the temperature range from 20 to 50 °C. The corrosion parameters and the adsorption isotherms were determined from the potentiodynamic polarization curves. It was found that the inhibitory efficiency (%) and the coverage rate () increase to a maximum of 87.97 at 25 °C in 10 mM of nicotinic acid at fixed temperature but decrease as the temperature of the solution increases. Nicotinic acid acts is a purely cathodic inhibitor. Moreover, the obtained thermodynamic parameters using Langmuir model suggested a physical adsorption type. A correlation was found between the corrosion inhibition efficiency and the theoretical parameters obtained by the functional density method B3LYP/ 6-31 + G (d, p). All these results indicate that the addition of NAC in the corrosive solution significantly decreases the corrosion rate.