Corrosion inhibition of Copper through two Tetrazole derivatives has been elucidated by means of Density Functional Theory (DFT) at the B3LYP/6-311G(d,p) basis set level. The calculated structural parameters were correlated to the inhibition efficiency of the frontier molecular orbital energies EHOMO (Energy of highest occupied molecular orbital), ELUMO (Energy of lowest unoccupied molecular orbital), energy gap (DE), dipole moment (μ), hardness (h), softness (s), the absolute electronegativity (c), the electrophilicity index (w) and the fraction of electrons transferred (DN) from the tetrazole molecule to Copper. The local reactivity has been analysed through the fukui and condensed softness indices in order to predict both the reactive centres and to know the possible sites of nucleophilic and electrophilic attack. The theoretical results, predicted using DFT-based reactivity indexes, are in good agreement with the published experimental results.