An efficient protocol for the synthesis of the Passerini adducts α-acyloxycarboxamides from aldehydes, isocyanides and water in a molecular ratio of 3 : 1 : 3 was described. The possible mechanism for the reaction was discussed by employing cross condensation and H₂¹⁸O isotope labeling experiments. This method offers a straightforward access to α-acyloxycarboxamides bearing two identical functional groups in high yields under mild conditions.