Benzotriazole derivatives, namely, N-[1-(benzotriazolo-1-yl)alkyl] aryl amine (BTMA), N-[1-(benzotriazolo-1-yl)aryl] aryl amine (BTBA), and 1-hydroxy methyl benzotriazole (HBTA), were synthesized and their inhibition behaviour on mild steel in 0.5 M H2SO4 at room temperature was investigated by various techniques. Preliminary screening of the inhibition efficiency (IE) was carried out using weight-loss measurements. Potentiodynamic polarization and AC impedance studies were used to investigate the inhibitor mechanism. Benzotriazole derivatives were found to act as mixed type inhibitors. Among the compounds studied, HBTA exhibited the best performance giving more than 95% IE in H2SO4 solutions. The passive film characterization was done using FTIR spectrum.