Thiourea dioxide in water was found to be an efficient and reusable organocatalytic system for the one-pot synthesis of polyhydroquinoline derivatives via the Hantzsch-type coupling of aldehyde, dimedone, acetoacetate, and ammonium acetate under mild reaction conditions. Operational simplicity, the use of an economically affordable catalyst, environmentally benign conditions, high product yields, and reusability of the catalyst system were the advantageous features of the developed method.