Direct spectroscopic evidence of a reaction occurring between acrolein and water and involving the exchange of an oxygen atom has been obtained by characterizing the non-covalently bound water complexes and their isotopic forms, via rotational spectroscopy. The experimental geometries of the binary and ternary water complexes have been determined, and other stationary points on the reaction path have been characterized using ab initio quantum chemical methods at the MP2/6-311++G(d,p) level. These results can enhance the understanding of the water-mediated atmospherically important reactions involving acrolein.