Caffeine, as a green catalyst, was found to be efficient for the synthesis of pyrano[2,3-c]pyrazoles by a four-component reaction of a mixture of hydrazine hydrate or phenyl hydrazine, ethyl acetoacetate, an aldehyde, and malononitrile in water at 50 ºC. The present protocol offers the advantages of a clean reaction, a short reaction time, a high product yield, and an environmentally friendly, reusable, easily-purified, and economically-available catalyst.