The aim of the present research is the evaluation of the extraction process effect on the chemical composition, the antioxidant activities, and the mild steel corrosion inhibition ability of Argania spinosa’s extracts (alimentary oil (AO) and hexanic extract of roasted almonds (HERA)). The chemical composition revealed that both extracts have the same major compounds: Palmitic, linoleic, and stearic acids, with their order slightly different. Electrochemical impedance spectroscopy (EIS), weight loss measurements, and polarization curves were used to estimate AO and HERA’s mild steel corrosion’s inhibition capacity. Based on these three methods, AO registered, respectively, 81%, 87%, and 87% inhibition efficiency while HERA registered 78%, 84%, and 82% inhibition efficiency. The antioxidant activity of AO and HERA was examined in parallel with standard antioxidants (gallic acid and quercetin) using two assays: DPPH* scavenging assay and ferric reducing antioxidant power assay (FRAP). AO had less EC₅₀ in both techniques (DPPH*: 3559.08 ± 161.75 μg/mL; FRAP 1288.58 ± 169.21 μg/mL) than HERA (DPPH*: 3621.43 ± 316.05 μg/mL; FRAP 1655.86 ± 240.18 μg/mL). Quantum chemical and molecular dynamic studies were employed to suggest the adsorption mechanism.