Quinazolinones are pharmacophoric scaffold present in various natural products and synthetic drugs. Quinazolinone is a heterocyclic chemical compound that contains a bicyclic structure, six-membered benzene and pyrimidine ring with a carbonyl group. Quinazolinones are important class in medicinal chemistry which possess with various therapeutic and biological activities including antibacterial and antifungal activity etc. This chapter consists of quinazolinone derivatives which possessing antimicrobial activity.