Synthesis of 3,4-dihydropyrimidinones/thiones, a multicomponent synthesis using ethyl acetoacetate, substituted aromatic aldehydes, and urea/thiourea has been carried out in presence of Mg–Al–CO 3 and Ca–Al–CO 3 hydrotalcite as a reusable solid catalyst. The work has been carried out under thermal solvent-free conditions without microwave irradiations, and under microwave irradiation. In this method excellent yield of 3,4-dihydropyrimidinones/thiones is reported in shorter duration. Hydrotalcites are non-toxic, easy to separate and recyclable catalyst hence making this process environment friendly. Mechanistic study of the reaction using hydrotalcites as catalyst has been studied under thermal conditions without microwave irradiations.