The present invention relates to a catalytic process for preparing pyrazoles of formula V comprising the step of cyclizing hydrazone substituted α,β-unsaturated carbonyl compounds by reacting them with hydrogen in a reaction mixture comprising as components (a) a hydrogenation catalyst, (b) an acid selected from Brønsted acids, ammonium salts of Brønsted acids, and Lewis acids, (c) a protic solvent, and optionally (d) an aprotic solvent.