Pyrido[2',1':2,3]imidazo[4,5-c]isoquinolin-5(6H)-ones such as the title compound, C(24)H(21)N(3)O(3), can be obtained in a few minutes in a microwave-assisted three-component reaction from 2-amino-pyridines, isocyanides and 2-carboxy-benz-aldehydes. In the title compound, the pyrido[2',1':2,3]imidazo[4,5-c]isoquinolin-5(6H)-one ring system is almost planar (mean deviation 0.068 Å). The dihedral angle between the benzyl ring and the pyrido[2',1':2,3]imidazo[4,5-c]isoquinolin-5(6H)-one ring system is 78.2°. The crystal structure is stabilized by inter-molecular C-H⋯O and C-H⋯N hydrogen bonds.