The importance of C–H···O hydrogen bonds involving the less common Re=O acceptor group in the small organometallic methyltrioxorhenium (MTO) is studied by combined vibrational spectroscopy and ab initio calculations. The observed vibrational spectrum is well described by the calculated spectrum of a C–H···O bonded dimer, which accounts for the symmetry decrease and the intermolecular interactions in the solid. Spectral evidence indicates both C–H···O and O–H···O hydrogen bonds are formed in the MTO/methanol solutions. The Re=O stretching mode is sensitive to hydrogen bonding, but the major effects of intermolecular association are observed in the βC–H and νC–H modes of MTO. Ab initio calculations for the MTO/methanol system predict the coexistence of both the Lewis adduct and the hydrogen-bonded complex, with an energy difference of ca. 1.2 kJ·mol¯¹.