Interactions of dimethyl sulfoxide with carbon dioxide and water molecules which induce 18 significantly stable complexes are thoroughly investigated. An addition of CO2 or H2O molecules into the DMSO⋯1CO2 and DMSO⋯1H2O systems leads to an increase in the stability of the resulting complexes, in which it is larger for a H2O addition than a CO2. The overall stabilization energy of the DMSO⋯1,2CO2 is mainly contributed by the S=O⋯C Lewis acid–base interaction, whereas the O − H⋯O hydrogen bond plays a significant role in stabilizing complexes of DMSO⋯1,2H2O and DMSO⋯1CO2⋯1H2O. Remarkably, the complexes of DMSO⋯2H2O are found to be more stable than DMSO⋯1CO2⋯1H2O and DMSO⋯2CO2. The level of the cooperativity of multiple interactions in ternary complexes tends to decrease in going from DMSO⋯2H2O to DMSO⋯1CO2⋯1H2O and finally to DMSO⋯2CO2. It is generally found that the red shift of the O − H bond involved in an O − H⋯O hydrogen bond increases while the blue shift of a C − H bond in a C − H⋯O hydrogen bond decreases when a cooperative effect occurs in ternary complexes as compared to those of the corresponding binary complexes. © 2018 Wiley Periodicals, Inc.