A new protocol for the synthesis of chromeno[b]pyridine derivatives is described via a three-component reaction of 4-aminocoumarin, aromatic aldehydes and malononitrile catalyzed by TiO₂ nanoparticles immobilized on carbon nanotubes (TiO₂-CNTs) as an efficient heterogeneous catalyst under ultrasonic irradiation in water. The sustainable and economic benefits of the protocol are the high yields of products, short reaction time, simple work-up procedure, and use of a non-toxic and reusable catalyst.