Display omitted •An eco-friendly drug losartan potassium (LP) is developed as a superior mixed-type inhibitor for steel corrosion.•The multi-anchored film of LP is formed on steel substrate.•Theoretical modelling provides deep insights into the inhibition performance of LP. The present study aimed to find a suitable alternative for traditional and hazardous corrosion inhibitors. A green antihypertensive drug-Losartan potassium (LP) with superior corrosion protection ability was developed for the first time. Gravimetric method, potentiodynamic polarization, AC impedance, and scanning vibrating electrode technique (SVET) were combined to evaluate the corresponding inhibition performance towards Q235 steel in HCl medium. The results indicated that LP exhibited superior mixed-type corrosion protection to steel at different temperatures owing to the formation of compact and ordered LP-adsorption film on steel surface. Specifically, the inhibition performance values increased to 88.9%, 91.8%, and 92.0% for 5 mM LP at 298, 308, and 318 K, respectively. Meanwhile, N-Fe bond from X-ray photoelectronic spectroscopy (XPS) implied multiple anchoring interaction between steel and LP with nitrogen atoms as active sites. Based on DFT calculation and molecular dynamics (MD) simulation, the obtained low energy gap (ΔE) and high Ebinding values as well as radial distribution function (RDF) analysis represented strong chemisorption of LP on Fe substrate, which theoretically explained the favorable inhibition effectiveness of LP compound at molecular or atomic level.