Mixing diisopropylamine and water releases some heat, indicating a small but negative enthalpy of mixing. The negative enthalpy of mixing means that the O-H-N hydrogen bond between water and DIPA has a slightly lower energy than the O-H-O hydrogen bond. This would account for the initial uptake of water into DIPA. However, our results show that, beyond water-DIPA dimers, larger molecular clusters immediately form that resemble dumbbell-like molecular cluster structures. Although in principle N-H-N hydrogen bonds could form between pairs of DIPA molecules in pure DIPA, this does not happen to any great extent, possibly due to steric hindrance.