The valence electronic excited states of Fe-2( CO)(9) have been studied using the time-dependent density functional theory ( TDDFT). Both tribridged D-3h and monobridged C-2V structures have been considered, and the structure of selected low-lying singlet and triplet excited states have been optimized on the basis of the TDDFT analytical gradient. Optimized excited-state geometries are used to obtain an insight into certain aspects of the Fe2( CO)(9) photochemistry. The Fe-2( CO)(9) ( D-3h) first triplet and second singlet excited states are unbound with respect to dibridged Fe-2( CO)(8) + CO, and the first two monobridged Fe-2( CO)(9) ( C-2V) singlet states are unbound with respect to the Fe( CO)(5) + Fe( CO)(4) dissociation. These results are discussed in light of the experimental data available.