The detailed dissociation mechanism of diborane (B2H6) in dimethyl sulfide (Me2S) media has been studied at the levels of B3LYP/6-311G**//B3LYP/6-31G* and B3PW91/6-311G**//B3PW91/6-31G*. All the calculations predict a two-step mechanism for the dissociation and only one II-bridge bond is broken in each. In comparison with the dissociation of B2H6 in vacuum or in hydrocarbon media, the participation of Me2S significantly lowers the activation barriers in the process. The barriers are even more lowered when solvent effect is embraced.