2-Mercaptoimidazole (2MI) is related to natural ovothiols that are recognized as powerful radical scavengers. Yet, despite early reports of its potent antioxidant properties, 2MI received little attention. Specifically, its radical scavenging activity against typical free radicals like HO• and HOO• has not yet been studied in terms of its mechanism and kinetics. In this project, density functional theory (DFT) simulations were used to assess the antiradical activity of 2MI. Calculations indicate that 2MI can demonstrate anti-HO• activity in both lipid and aqueous environments (koverall of 1.05 × 1010 and 2.07 × 1010 M-1 s-1, respectively). The calculated kinetics is extremely close to the experimental data in water (pH = 7.0), resulting in a kcalculated/kexperimental ratio of 1.73, validating the accuracy of the computational method and its usefulness for assessing radical scavenging activity in silico. In lipid media, the HOO• radical scavenging activity of 2MI is faster than that of common typical natural scavengers such as ascorbic acid, Trolox, and trans-resveratrol; hence, 2MI is a powerful radical scavenger in nonpolar media.