Quinazolinones, an important class of heterocyclic compounds, have been widely used in pharmaceuticals because of their biological activity. However, the efficient and economical synthesis of quinazolinones has remained a challenge. A novel synthetic approach has now been developed to produce quinazolinones from olefins, CO, and amines over heterogeneous Ru‐clusters/ceria catalyst in the absence of acids, bases, and oxidants. Furthermore, H
2O is generated as the only by‐product. A series of quinazolinones with aromatic or non‐aromatic substituents can be obtained in yields of up to 99 %. The Ru‐clusters/ceria can be reused at least four times. The analysis of the E‐factor (environmental impact factor) for the synthesis of 2‐ethyl quinazolinone suggests that this system is more environmentally friendly than other processes reported previously.