In the present paper, we report the successful synthesis of zinc aluminate nanoparticles by the co-precipitation method using aqueous ammonia solution as the precipitating agent. ZnAl₂O₄ nanoparticles have been used as an efficient catalyst for the preparation of 4,4′-(arylmethylene)bis(3-methyl-1H-pyrazol-5-ol) derivatives by pseudo five-component reaction of hydrazine hydrate, ethyl acetoacetate and aldehydes at 60 °C in water. Atom economy, wide range of products, excellent yields in short time and environmental benignity are some of the important features of this protocol.