The 1,2,4-triazoles are an important group of medicinal substances which exhibit a wide range of activity, such as analgesic, antibacterial, fungicidal, antinflammatory, antiviral and anticancer. As a part of our long-term study on 1,2,4- triazoles we synthesize 4-benzyl-3-[(1-methylpyrrol-2-yl)methyl]-4,5-dihydro-1H-1,2,4-triazol-5-one which is characterized with anticancer activity. Here, we present an exhaustive studies of its electronic and molecular structure, aimed to rationalize the observed pharmacological activity, supported by the molecular docking to the EGFR kinase domain ATP binding site. The structural studies include X-ray analysis, experimental and computed spectral analysis (1H and 13C NMR, IR) as well as conformational analysis and the frontal molecular orbitals (FMO) analysis. The results of molecular docking indicate that interaction of 4-benzyl-3-[(1-methylpyrrol-2-yl)methyl]-4,5-dihydro-1H-1,2,4-triazol-5-one with the EGFR kinase domain ATP binding site may be responsible for the observed anticancer activity of this 1,2,4-triazole derivative. Moreover, we find that formation of the respective ligand-protein complex is conditioned by the keto-enol tautomerism of the ligand, i.e. the energetic prevalence of the keto form.