The inhibition effect of synthesized corrosion inhibitor namely 5,5′-(1,4-phenylene)bis([Formula: see text]-phenyl-1,3,4-thiadiazol-2-amine) (PBPA) on the corrosion of mild steel in 1-M hydrochloric acid environment are examined by gravimetric techniques at various temperature (303–343 K). The synthesized inhibitor concentrations are 0.1–0.5[Formula: see text]mM. The inhibition efficiency increased with the increase of the inhibitor concentration. The inhibition efficiency reached 94% at the highest studied concentration of 0.5[Formula: see text]mM for 5[Formula: see text]h of immersion time and 303[Formula: see text]K. Moreover, the inhibition efficiency decreased with the temperature increase. The adsorption of tested inhibitor molecules on the surface of mild steel follows the Langmuir adsorption isotherm. The studied inhibitor molecules showed excellent inhibition since PBPA molecules have nitrogen and sulfur atoms in addition to phenyl and thiadiazol rings which were linked together in conjugation system.