A convenient synthesis of pyrimidinthiones was carried out in presence of thiourea and easily available catalyst sulfamic acid (2a-t). One-pot Biginelli reaction is very important due to the use of simple and readily available chemicals, less reaction time, economically friendly, and furnishing good yield.Structures of the synthesized compounds are characterized by spectral techniques like IR, 1 H-NMR, 13 C-NMR, and LC-MS. Synthesized compounds were studied for their antimicrobial activity against several strains of bacteria (E. coli, P. aeruginosa, and S. aureus, S. pyogenes) and fungi (C. albicans, A. niger, and A. clavatus) using serial dilution method.