The title compound 4-(3-methoxyphenyl)-3-(2-thienylmethyl)-4,5-dihydro-3H-1,2,4-triazole-3-selone 2 was synthesized by two-step procedure including condensation of 1-isoselenocyanato-3-methoxybenzene with 2-(2-thienyl)acetohydrazide to selenosemicarbazide 1 and its intramolecular cyclization. Oxidation of selone 2 by atmospheric oxygen or hydrogen peroxide furnished corresponding diselenide 3 or product of elimination of selenium 1,2,4-triazole 4. Alkylation of compound 2 by benzyl chloride leads to the formation of selenide 5. The synthesized compounds have been characterized by spectroscopic techniques and the structures of 3,4 and 5 were confirmed by X-ray diffraction techniques and the supramolecular contacts were analyzed by Hirshfeld surface analyses. © 2020 Elsevier B.V.