The corrosion deterrence as well as antifouling efficiency of Ailanthus excelsa leaf extract (AELE) was explored against mild steel in an acidic environment. The AELE was tested for standard corrosion measurement techniques such as weight loss method, electrochemical impedance spectroscopy analysis (EIS), potentiodynamic polarization (PP) and SEM. Further, UV–vis and FTIR screening were carried out for the determination of corrosion inhibition mechanism. Adsorption isotherm models, electrochemical techniques, spectroscopic (UV–vis and FTIR) and surface morphological studies (SEM) well confirms the adherence and corrosion inhibiting nature of AELE inhibitor. AELE exhibits potential inhibition of ∼96 % on mild steel up to 1.5 mL at 308 K in weight loss method, which is in good agreement with EIS and PP measurements. The AELE was also tested against fouling bacteria, which showed a significant inhibition zone between 12 mm and 21 mm against Staphylococcus sp. The antifouling mechanism of AELE against fouling bacteria was found potentially effective, which also provides new insights to investigate AELE’s antifouling property in existing research.