Owing to the depletion of light sweet crude, high-temperature corrosion by sulfidation and naphthenic acids in the oil phase has become one of major challenges for crude oil refineries. The corrosion by model sulfur compounds and naphthenic acids has been extensively studied in laboratories, but the effect of thiophenes, which are widely present in crude oil, is often ignored due to their noncorrosiveness. In the current study, sulfidation and naphthenic acid corrosion are studied in the presence/absence of two model thiophenes, dibenzothiophene and benzothiophene. It is found that thiophenes show an inhibitory effect on naphthenic acid corrosion while not deterring sulfidation significantly. It was proposed that naphthenic acid may corrode the steel, generating iron naphthenates underneath an adsorption layer of thiophenes and producing magnetite.