The interactions of low-energy (20–800 eV) nitrogen ions with Cu(100) at room temperature have been investigated by using temperature programmed desorption (TPD) mass spectrometry and high-resolution electron energy loss spectroscopy. The desorption feature observed at 760 K can be attributed to adsorption of surface atomic nitrogen on fourfold-hollow sites. When the impact energy (IE) of the nitrogen ions used for the irradiation exceeded 75 eV, our TPD results further revealed a new desorption feature at 520 K, which can be tentatively assigned to ion-implanted atomic and/or molecular nitrogen. The intensities and temperatures of the desorption maxima of the surface (chemisorption) and ion-implantation (entrapment) features were found to greatly depend on the IE and the dosage of the ions. Other effects including the creation of defect sites as a result of the ion irradiation are also investigated.