The 1,3-dipolar cycloadditions of diazomethane and diazoethane with methyl 3-(diethylamino)propiolate were investigated experimentally and computationally by employing density functional theory (DFT). The experiments provided methyl 3-(diethylamino)-pyrazole-4-carboxylates as the only isolated regioisomers. The constitution of these cycloadducts was secured by independent synthesis and decarboxylation