The effects of 2-hydroxy-1-naphthaldehyde glycine (HNG) and 2-hydroxy-1-naphthaldehyde (HN) on the corrosion of mild steel in hydrochloric acid have been studied. Weight loss measurements reveal that HNG exhibits higher inhibition efficiency than HN. Generally, inhibition was found to increase with increase in inhibitor concentration and temperature. Chemical adsorption mechanism has been proposed for the inhibitors. The inhibitors obey Langmuir adsorption isotherm at higher concentration and temperature. The difference in the inhibition behaviour of the compounds has been explained in terms of the solubility of the compounds and strength of the inhibitor-metal bond rather than difference in molecular weights alone.