Trinuclear transition-metal carbonyl complex dodecacarbonyl triruthenium (Ru3(CO)12) is considered as one of the paradigms in cluster chemistry, which plays an important role in photocatalysis, photoenergy conversion, and synthetic chemistry. Due to structural symmetry (D3h point group), 12 carbonyl (C≡O) groups in the Ru3(CO)12 complex contribute to mainly three excitonic carbonyl stretching modes: E' (radial), A2″ (axial), and E' (axial). In this work, efficient intramolecular vibrational energy redistribution (IVR) processes among the three modes in this Ru-CO complex were observed to occur on the time scale of tens of picoseconds. The IVR processes were characterized in detail using a kinetic model and fitting to the waiting-time-dependent diagonal and off-diagonal signals of ultrafast two-dimensional infrared spectroscopy. In addition, the diagonal anharmonicities of the three C≡O stretching modes were determined to be quite close to one another, and the coupling-induced cross peaks were invariant because this Ru3(CO)12 cluster does not show picosecond fluxionality and hence their contributions were neglected in modeling the IVR processes. Our results provide a benchmark for understanding the excitonic nature of the vibrational excited states of the carbonyl vibrators and the associated efficient vibrational energy-flow pathways, in such multicentered transition-metal complexes, which are of key importance to their functions.