A series of new pyrimidine, triazine, and isoindole heterocycles fused to the selenolopyrazole ring system was synthesized by various condensation reactions of the amino selenolopyrazole carboxamide 1, which was performed by a new green methodology. The pyrimidinone compound 6 was used as a versatile precursor for several aromatic nucleophilic substitution reactions to produce the sulfanyl pyrimidines 10a‐c and the corresponding amines 11a‐c and 12a, b. Assignment of the chemical structures for the newly synthesized compounds was confirmed by elemental and spectral analyses including Fourier transform infrared (FTIR), 1H‐NMR, and 13C‐NMR and mass spectroscopy for some of them. Furthermore, some of these compounds were screened against various pathogenic bacterial and fungal strains. Their results demonstrated that some of them revealed remarkable antimicrobial activities.