Abstract: Three new organoselenium compounds are synthesized: N-phenyl-2-(2-thienylacetyl)hydrazinecarboselenoamide (I), 4-phenyl-5-(2-thienylmethyl)-2,4-dihydro-3H-1,2,4-triazole-3-selone (II), and 3,3'-di[4-phenyl-5-(2-thienylmethyl)-4H-1,2,4-triazolyl] diselenide (III). Two of them (compounds II and III) are characterized by X-ray diffraction analysis (CIF files CCDC nos. 1956602 (II) and 1956603 (III)). Compound II crystallizes in the monoclinic crystal system (space group P21/n) with two crystallographically independent molecules A and B being different conformers relative to rotation about the NTrz–CTrz–C(H2)–CTph bond, where Trz is triazole and Tph is thiophene (gauche-A (51.4(3)°) and cis-B (4.2(4)°)). In the crystal of compound II, molecules A and B form chains along the crystallographic axis a due to strong hydrogen bonds N–H···Se. Then the chains are bound into a three-dimensional framework via intermolecular nonvalent interactions Se···S (3.3857(11) Å). Owing to the anomeric effect, diselenide III is characterized by the typical gauche conformation of the substituents at the Se–Se bond (torsion angle СSeSeС 83.5(4)°) stabilized by a weak intramolecular hydrogen bond С–H···π. In the crystal of compound III, the molecules form chains along the crystallographic acid b due to intermolecular noncovalent interactions Se···π(C–C) (3.404(6) and 3.458(12) Å), Se···Se (3.8975(11) Å), and S···N (3.250(5) Å). Bactericidal and fungicidal activity of the synthesized compounds is studied. © 2021, Pleiades Publishing, Ltd.