In the presence of Et₃N, the [3 + 2] cycloaddition of isatins, 2-(aminomethyl)pyridine and isatin-based imines proceeded readily, and furnished novel imidazolidine-dispirooxindoles in up to 84% yield with up to >99 : 1 diastereoselectivity. The relative configuration of the imidazolidine-dispirooxindoles was firmly confirmed on the basis of X-ray single crystal structure analysis. The reaction mechanism was assumed to account for the diastereoselective formation of the imidazolidine-dispirooxindoles.