The reaction mechanism on the formation of the hydrosulfido complex [Re(SH)(CO)(3)(bipy)] via the reaction of [Re(OH)(CO)(3)(bipy)] with carbon disulfide was theoretically investigated at the B3LYP/6-31+G(d,p) (LANL2DZ+f for Re) level of theory taking into account bulk solvent effects by using the PCM-UAHF continuum model. The energetics of the process was also analyzed by means of single-point energy calculations by replacing the B3LYP functional by the B3PW91, M05, TPSS and TPSSh ones. The most favored mechanistic routes obtained by us uncover all the molecular rearrangements involved in the reactive process, thus allowing the enriching of the experimental mechanistic proposal. Besides, our findings permit to explain the assignment of the solution color change to the formation of [Re(SH)(CO)(3)(bipy)] when mixed CS(2) with [Re(OH)(CO)(3)(bipy)]. Finally, based on our mechanistic study is also possible to rationalize the formation of [Re(SC(S)OCH(3))(CO)(3)(bipy)] when [Re(OCH(3))(CO)(3)(bipy)] reacts with CS(2) and of TpZn-OCH(3) when methanol is present in the reaction of TpZn-OH with CS(2).