One-pot condensation of pyrazole-4-aldehydes and hydroxylamine hydrochloride to form thecorresponding oxime using formic acid as a medium and further dehydration of oxime using a catalyticamount of orthophosphoric acid to afford novel pyrazole-4-carbonitrile. This protocol serves as an orthophosphoricacid-catalyzed one-pot conversion of aldehyde to nitrile. Most remarkable features of this methodare metal-free, cost-effective, atom efficiency with excellent yield (98–99%). This process will serve as arobust and scalable tool for the synthesis of valuable and versatile precursor (nitriles). This precursor willpave the way for the synthesis of various medicinally important valuable compounds.